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MFI SIG 556 Swiss Style 550 / 551 / 552 / 553 / 55x Rear Diopter Sight & Rail (with Fiber Optic Rear) with Choice of Front Sights or No Front Sight (BLACK) / Price Includes S&H via Priority Mail.

Designed specifically to fit the SIG 556 & SIG 551A1 Series Rifles & Pistols.

Limited Supply: only 3 remaining
Was: $395.00
Sale: $245.00
Save: 38%
Save: $150.00
5 5 2

Customize Your Item

- Add a Front Sight Option -
 * required
- Add or Subtract a Fiber Optic Op -
 * required
- No Export / US DOS or US DOC -
 * required
SHIPPING IS INCLUDED VIA USPS on orders over $82.00 Dollars AND OR If S&H is INCLUDED in the Title / Discription.


NOTE: This product is identical to the 1st Production with the exception that the round slotted windage adjustment wheel on the rear sight is now Mil. Spec. Parkerized Medium Gray instead of Mil Spec Black Oxide as you see in the photos. Once I have a chance to take new photos I will add them and delete the old photos.

NOTE: The MFI Diopter Rail Sight Combination is the CORRECT height for the Original Swiss SIG SANs Front Sights OR the MFI Hooded or SANs Flip Front Sights.

NO OTHER sights that I know of will work / be the correct height.

It will NOT work with the SIG USA front hooded sight that is tall and has a slant to the rear.

The price you see above reflects the "Cadillac Version" with a Front Hooded Sight Included. By clicking the drop down lists “Customize Your Item” you will either choose the Cadillac / Full Blown Set or be allowed to (Opt Out) and save money.

So yes this is a set you are buying unless you choose not to.

This product is a True Plug & Play item. Just unscrew the 3 bolts that hold your rail on and place our rail on in it's place. There are no small metal tabs or shims to lose as ours is 100% self contained. We also provide 3 replacement bolts and an Allan Key Wrench.

The Rear Diopter Sight had to be connected to a rail in order for it to be low enough to line up with the ultra low profile of the Original Swiss SIG SANs Front Sights. Yes you can use the Original PE90 / 550 / 551 / 552 / 553 Swiss SIG Front Hooded or Non-Hooded Sights. You can NOT use the SIG 556 USA Hooded Front Sight or any other sight on the market except our MFI SIG SANs Hooded or Non-Hooded front sights.

If you want to see a video that a customer posted on the Diopter Rail click below:

MFI REAR Diopter Sight & Rail:

I designed these to look like the original SIG PE-90 / SG 551 rear diopter sights that were welded on to the receivers. The parts are NOT exact copies of the originals… Meaning that the parts of the MFI Rear Sight are NOT interchangeable with the original Swiss SANs parts. The design did not allow this and it was more cost effective to not even try.

The Rear Diopter functions exactly like the original and has the exact same markings as the Swiss SANs sight housing. The markings on the Drum / Diopter are also an exact copy of the original with the exception of the #4 which we changed from white to red… it just looked cooler.

As I am not a huge believer in the accuracy of the .223 / 5.56mm cartridge so I only fully tested the number 1 position at 100m. The #2, 3 and 4 designations may or may not be applicable. I did position the holes in the correct location, but not having the time or funds to waste on something I do not really believe in. While the #2 and #3 holes are the right size and position the #3/4 position hole is much smaller than the original and is NOT threaded for the insert of a target peep sight, nor is it likely to be at the correct angle as I do not have one to check against. The Diopter walls have not been counter bored on the inside either, so the walls are thick in that area to accept a thread. As I said... The hole is much smaller so that the customer could MILL a new hole at whatever angle they need and make it work. Sorry you are on your own on this one... just not cost effective to test / check 100% when 99% of the customers will never have the money to buy a SIG SANs target peep sight much less have the need to use it.

Fiber Optic Option: The holes for the fiber optic option in the rear Diopter are also smaller than the original. I did this so that you could buy the sight without the fiber optic and drill the holes out to fit the Tritium Ampules / Tritium Inserts. Due to the short shelf life, cost and pain in the ass import regulations I have no intention of ever offering Tritium anything for sale. Check the forums for suppliers.

Above is a photo showing you the two options side by side (with or without fiber optic).

Materials of Construction:

The Rail, Diopter & Diopter Sled are 4000 series cast aluminum. NOTE: As with all castings there will be some deflection / minor cosmetic defects that are hardly noticeable to the naked eye and consist mainly of tiny pits in the very rear of the rail or perhaps tiny imperfections on a few of the leading edges of the 1913 main section of the rail. None of these detract from the functionality of the product. Just nature of the beast when it comes to castings.

The Windage adjustment wheel and other small parts are steel.

Finish: The Rear Sight & Rail are painted to match SIG 556 Black Finish. The Rear Sight is made from special 4000 series aluminum alloy to allow it to flow more consistently into a mold. Unfortunately the non-aluminum alloys used (in particular copper and silica) make it impossible to anodize, so the rear sight and rail are painted like the originals were. The rear sight housing and rail are near 99% finished when they come out of the mold. We tried to retain many of the casting marks and even simulated some of the grind markings found on the original sight housings. I am not aiming for 100% perfection in a product as that is pointless and no cost effective. So if you have a safe queen that is worshipped rather than used... no MFI product is likely to live up to your standards.

At the front of the rail you will see a Swiss Style Cross and Shield. Additionally we have shaped the front of the rail to have a similar cut out that would normally be used for a scope mount, but in this case is strictly cosmetic. I spend a lot of time on the finer points of the design as it is critical to make any product as cool looking as possible. I hope you all approve.

Comes with: 3 – MFI SIG Top Rail Bolts and Allan Key

NOTE: Copying the original as closely as we did has it's advantages and disadvantages. While we try to maintain the look and style of the original rear sight any deficiencies that exist in the original design will likely come through as well on the reproduction. A good case in point is the Windage Adjustment Knob. Originally designed to use a Swiss Franc Coin to adjust, even the original SANs sights get the paint chipped or the edges of the adjustment slot scratched or damaged in some manner. For this reason we recommend that you adjust the knob by hand (yes possible) to avoid damaging the finish of the knob. The next best option is to use a coin (dime) with thin tape on it. The coin is what was originally used as the slot is dished to receive the rounded edge of a coin and NOT the flat edge of a screw driver.

MFI SIG Diopter & SIG SANs Swiss Original welded on Diopter. vs. SIG USA Clip on Rear Diopter:

The MFI Diopter is attached (molded into the rail as one piecee) to the rail as it is otherwise impossible to get to the same super low profile as the Original SIG SANs Swiss height, which was achieved by welding the diopter directly to the top of the receiver. The MFI Diopter is at the exact same height as the original Swiss sight so you can even use an original front Swiss sight if you can find one.

SIG USA which produced the SIG 556 rifle is NOT the same company as SIG Germany or SIG Switzerland and they have no relationship in regards to the 556 platform. The Clip on Diopter they produced is at least twice as tall as the original SIG SANs Swiss and therefore no component of that sight can be used with either the Swiss or MFI rear sights.

The SIG USA Clip on rear diopter is also made of some inferior pot metal and extreme care needs to be used when tightening down the rail locking screw as it can crack the base of the sight, strip the screw or nut or the bolt can be pulled out of the opposite side of the sight base.

As for modification of the MFI Diopter to be a clip on variation. No it is IMPOSSIBLE to make any clip on that would be at the correct height without also cutting off the rail of the rifle and somehow bonding it to the top of the receiver.

If it were possible to make a clip on version I would have made one.

MFI Front Hooded SIG 550/1/2/3 Sight: IS AVAILABLE

Here is a link for photos and information (same as below) with prices if you wanted to order separately:

As mentioned the price on this page reflects the INCLUSION of a Front Sight. I will cover the basics of the Hooded Sight here as that is what most of you are looking for.

The non-hooded version has it's own page:

The MFI Front Hooded SIG 550/1/2/3 Swiss Style Sight is basically a direct copy of the original except in aluminum. The sight main body and flip up blade are made from 7071 T-6 Aircraft grade aluminum and are precision CNC. I choose aluminum over steel due to the cost effectiveness and versatility of the material. Obviously it would be pointless to make an identical sight to the original & have it be the same price or even more expensive. Additionally 7071 T-6 aluminum can accept a Military Spec. Hard Coat Anodized Finish making it very durable. The cross over windage adjustment wheel / donut and bolt are weapons grade steel and have a Mil. Spec. Black Oxi coating.

The Front Sight Fiber Optic Blade that flips up and down is interchangeable with an Original Swiss SANs Flip Up Blade with the Tritium insert. So “Yes” you can swap out the MFI blade for a SIG one if you so choose. Note that like all flip up fiber optic or tritium blades... the MFI blade is taller than the stationary front post / blade. I am not sure why SIG and for that matter everyone on the planet does this… I just choose to follow suit. In our case it does allow more light in and thus makes for a much brighter aiming point.

The Finish on the MFI Front sight is black only. This is because of the volume we expect to do is 95% black rails. Hard coat anodizing takes paint very well so if you want yours to be painted. Have at it... Personally I have always had an issue with the heavy coat of paint found on the original Swiss SANs sights (front and rear). Anodizing just looks so much more professional and clean.

The Front Sights comes with the Windage Adjustment Wheel and Allen Key. For those of you with Optics only weapons or do not currently have a front sight... The installation is a bit tedious... Go to this link for full instructions and tips.

Go to this page for Instructions on the installation of the front sight. Click on the "Instructions" tab:

Attention Quad Rail Owners: I have been informed by one Quad Rail owner that our Diopter rail does not fit plug and play with is 556P (Pistol Rail). The owner told me that it looks like he has to remove 0.0650" of either the MFI rail or the Quad rail to make it fit.

Sorry I never expected anyone with a quad rail to want one of these as this is a Retro Design. I designed this specifically to fit the Swiss SANs 551 or MFI 556P/2 Hand Guards and to be tight so as to eliminate some of the movement "slop" of the hand guard. I have tested the original SIG USA "SIG 556 Fish Gill" hand guard and the SIG USA Classic / SIG 556 / 551A1 hand guards and they fit fine as well.

So, Yes the MFI SIG 550 Style Diopter Sight & Rail is a hair longer than the stock SIG USA 556 rail. Again this will be a very tight fit for the 3 hand guards I mentioned. Going on is easy as you just press down, coming off is a little harder and in either case you can if you want undo the Diopter Rail (nothing falls out of the bottom like the SIG 556 rail thumb nail does) and reattach the rail. You will not lose zero on the iron sights as the tolerances of the 3 hole set up are very tight.

This will NOT fit the 4 Bolt Rails found on the first 400 SIG 556s produced.


In accordance with the Joe Biden & Beto O’Rourke directive I personally as well my company no longer own(s) or possess any firearms or ammunition. This includes but is not limited to: Handguns, Pistols, Shotguns, Rifles, NFA items, Hog Legs, Fire Sticks, Smoke Poles and or Thunder Clubs.

All firearms that appear on our web site, regardless of what is written about them, are not owned by the company nor possessed by anyone associated with MFI and may even be CGI / PhotoShop.

Therefore regardless of any new firearms laws / taxes, no probable cause can EVER be assumed on any property (stationary or mobile) owed by myself or MFI.

AGAIN: We are 100% in compliance with any possible new “Biden / O’Rourke Public Safety Act” and therefore NO PROBABLE CAUSE could ever be assumed.

Lastly anyone arriving with a warrant of any kind will be assumed to be an IMPOSTER with intent on murdering us and will be treated as such without warning.

Those invading our territory may receive serious and even fatal wounds from rusty blades, clubs with bent nails, spear tips, arrows and or crossbow bolts.


This item is NOT RESTRICTED FOR DOMESTIC US SALES in any way and we offer DOMESTIC USA shipping to ANYONE. We ship to all 50 US States as well as all US Territories i.e. Guam & Puerto Rico. Sorry we can NOT ship to ANY APO address regardless of actual location.

This item is 100% RESTRICTED FOR EXPORT OUTSIDE THE USA. The US Department of State regulates / restricts this product and it is NOT EXPORTABLE outside the USA even to LE, Governments or Military without State Department approval.

This approval is AVAILABLE through MFI as we are an ITAR / Dept. of State Registrant with the Directorate of Defense and Trade Controls Office. We can obtain a US State Dept. Export License for you.

Please feel free to contact us if you have any questions on this issue.

Shipping Information

  • Item Requires Shipping
  • 1.1 lbs.
  • SHIPPING IS INCLUDED VIA USPS on orders over $82.00 Dollars AND OR If S&H is INCLUDED in the Title / Discription.

Customer Reviews

Comment Total Reviews (2)

Top Quality and fast shipment as always
  • Currently 5/5 Stars

Reviewed by:

Product ownership: Less than 1 week

Purchased from: MFIAP.COM

This is an awesome piece to add to my SAN 553R

Great rail
  • Currently 5/5 Stars

Reviewed by:

Product ownership: Less than 1 month

Purchased from: MFIAP.COM

I love this rail. It looks fantastic. I got the hooded front sight and both front and rear sights with the fiber optic for my sig P556. I removed my red dot sight, removed the old rail, installed the new rail, and reinstalled the red dot sight. I got out my laser boresighter and did not have to adjust a thing. Everything lined up perfectly. Fantastic product.

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