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MFI SIG 556 MAD / BUIS Flip Up Rear Sight / Price Includes S&H via USPS 1st Class Mail. / DISCONTINUED FOREVER!

Designed specifically to fit the SIG 556 & SIG 522 Series Rifles & Pistols.


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NOT FOR USE ON SIG 556R / 7.62X39

Due to the added recoil for the 7.62X39 round we do not recommend thr MAD REAR FLIP UP SIGHT as the rear flip up part can at times drop down (to the stored position) under the added recoil of the .30 caliber round. We have had customers with 556Rs buy these and modify them slightly by deepening the channel that the detent sits in and or replacing the spring with a stronger one.

This issue is ONLY with the MAD Rear sight. ALL FRONT SIGHTS are 100% OK to use with any caliber.

MFI SIG 556 / 522 / 551A1 Flip Up Rear Site aka: Ghost Sight

MAD (Multiple Aperture Device)
BUIS (Back Up Iron Sight):
Fits All SIG 556 Series Receivers:

Will NOT line up with SIG USA Classic Hooded Front (with a slant). This lines up with the Original SIG USA Non-Hooded Front Flip Sight or MFI Copy of the Original SIG USA Non-Hooded Front Flip Sight. It does not line up with anything else as that is a unique height that SIG USA invented.

The MFI Flip Up Rear SIG Site aka: Ghost Sight / MAD (Multiple Aperture Device) / BUIS (Back Up Iron Sight) is a copy of a non-patented iron site that was originally developed for Naval Surface Warfare Group. The requirement was for low profile back up iron sight that provided a wide range of aperture sizes that could be flipped up and down.

This device has four apertures: 0.092, 0.127, 0.166 & 0.210. It achieves this by rotating the aperture disc in either direction to bring the next size into view. All apertures are on the same plane and are thus zeroed to the same point of impact. The aperture disc is knurled for easier manipulation in combat environments.

A standard military M16 windage knob is utilized for familiarity. One click of the windage knob provides approximately 0.50 MOA change when mounted on the SIG 556 rifle.

The mount body is CNC manufactured from aircraft grade 6061 T6 aluminum and anodized in a non-reflective black mil spec finish. The Flip UP Portion which contains the aperture disc is made from weapons grade steel alloy for longer life. All attachment hardware & bolts are grade 4 steel.

The flip up stem / aperture of the site is designed to sit at the rear of the receiver with the small aperture bolt resting on the top rail (slightly raised). This allows the user fast and easy access to the backup weapons sight in even the harshest conditions or while wearing gloves. The sight locks up or down via a fast / quick roller bearing with spring assist. These is deliberately NOT a 100% locked / requiring a button to be pressed to raise or lower the sight. We do this as these are considered BACK UP sights and need to be raised and lowered without much effort. The Roller Bearing lock with spring assist keeps the flip up aperture either up or down even during recoil in Full Automatic Firing Mode.

Again real world solutions for real world operations.

NOTE: There are a few non-functional / cosmetic things to this sight to note. These do NOT effect the stability, accuracy or any issue with proper functionality of the sight. We mention these just so you are aware that they exist on all our SIG MAD sights. All of these stem from designing a sight far lower in profile than ever before while at the same time trying to be as cost effective as possible without sacrificing quality or performance.

Again we are trying to offer a Cost Effective Back Up Sight Solution for the SIG 556 and 522 (.22 Long Rifle) calibered guns. In other words we are offering a Complete Set of Front and Rear Sights for Less than $125.00!

ELEVATION NOTE: There is no elevation adjustment for these sights... just not cost effective and most back up sights do not have elevation adjustment. So we have point of impact set for 100m to 150m for .223 and 50m to 75m for .22LR.

  • The head / stem / part with the aperture that sticks up will have some play side to side if you place your finger on either side and push. This is 100% normal as the stem is on a threaded rod and in order for it to more freely side to side there must be some slight degree of deflection on the threads. The stem will return freely to the center position when released. Even if you were to keep pressing it while shooting the total angle of deflection at 100 meters would NOT cause your bullet to impact more than 1/2 inch away from where it normally would have landed.
  • The head / stem / part with the aperture when it lays down may or may not appear to be at a straight 90 degree angle. This is caused by the fact that there is a single ball bearing that makes contact with the slot on the bottom of the stem. The ball baring is in a stationary detent so depending on where the stem is located from windage (right or lift of dead center) may cause the stem to appear to tilt one way or the other. Like the aforementioned issue, this is because the stem rides on a threaded rod. Regardless of any angle in the down position this does NOT affect the use as the sight cannot be looked through anyway.
  • Yes we are 100% aware that both of the above could be solved by making the stem wider where it rides on the threaded rod. The problem is if we make it wider we lose a significant range of motion right to left on the rod which means you lose windage adjustment. Likewise increasing the base to accommodate greater movement and un-necessary stability not only increases the width of the base (which is already wider than the top rail), but also cost.
  • Again we are NOT trying to make the END ALL GREATEST MAD SIGHT OF ALL TIME... We are trying to make the Best Possible & Functional MAD Sight that we can for less than $70.00.

MFI SIG 556 / 551 A1 / 522 Flip Up Rear MAD Weapons Sight Comes With:

  • 1 - MAD Flip Sight
  • 1 - Allen Key


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.


  • The main housing is made of 6061-T6 AIRCRAFT GRADE ALUMINUM.

  • The Flip Up Head & Adjustable Aperture is Weapons Grade STEEL.

  • The Windage Adjustment Bolt is Grade 4 STEEL.

  • The Cross Over / Locking Bolt is Grade 4 STEEL.

  • Fits all SIG 556 Series Weapons with Flat Top Receivers. Fits any Mil. Spec. 1913 Picatinny / Weaver rail.

  • Overall Length: Flipped Down @ 1.990 Inches / 50.7mm or Flipped Upright @ 1.120 Inches / 30.2mm

  • Height: Flipped Down @ 0.525 Inches / 13.3mm (from the top of the rail)

  • 100% Mil. Spec. 1913 Picatinny: Fits to any Weaver or Picatinny Rail.

  • Aperture Sizes: Standard Mil. Spec. @ 0.092, 0.127, 0.166 & 0.210

  • Weight: 1.90 oz

  • Co-Witnesses with ONLY: Original SIG USA 556 Tall Flip Up Front Sight or MFI 556 Flip Up Front Sight.

  • Cost Effective: Highest Quality at the lowest price is always our goal. This equates to greater profits for distributors and re sellers. Nothing else on the market compares in versatility, quality and cost effectiveness.

ELEVATION NOTE: There is no elevation adjustment for these sights... just not cost effective and most back up sights do not have elevation adjustment. So we have point of impact set for 100m to 150m for .223 and 50m to 75m for .22LR.

NOTE: All Hex Key / Allan Head Bolts are metric. We choose metric sizes mainly because the Original Swiss SIG SANs Front Sight (which we mimic in every way) uses a windage Hex Bolt / Allan Key that is 4mm in size. While we do supply the Allan Key / Hex Key for the MAD Sight's attachment to the rail we also have 2 other metric screws or bolts in use on the MAD sight. So here are all the sizes for you to use as a quick reference.

  • MFI SIG Front Flip Sight Windage Adjustment Bolt is 4mm.

  • MFI SIG Rear MAD Sight Attachment Bolt is 3mm.

  • MFI SIG Rear MAD Sight Windage Knob Bolt that holds the side know onto the thread rod is 1.5mm.

  • MFI SIG Rear MAD Sight Stem / Flip Up Portion Bolt that holds the back plate on is 2mm.


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
  • 0.2 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 (1)

Perfect fit... nice product
  • Currently 5/5 Stars

Reviewed by:

Product ownership: Less than 3 months

Purchased from: MFIAP.COM

I wish it had an elevation adjustment, but the point of impact that MFI staes is 100% dead on!! 100 meters and a 1.5" group!! Flips up and down well... on and off in seconds... took only 3 days to arrive!!!



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