Front Sight Base (FSB) for all fix sight US Military M16 versions.
To get the right version, you first need to decide which Gas Block size you need (.625 or .750).
- .625 is for "Pencil" profile barrels, measured as .625 inches in diameter at the Gas Block location on your barrel (diameter of barrel at the gas hole location).
- .750 is the size used on most barrels today (since 1984 or so). Standard M16A2 / M4 profile size.
Second, choose which height you need:
- Non-F marked is for all carry handle models (AR15, M16, M16A1, M16A2, XM177, Commando, etc.).
- F Marked is for flat tops.
Last, choose if you need the Bayonet Lug shaved off or not.
- Only versions officially with shaved bayo lugs are the short SMG/Commando versions , e.g. XM177, GAU-5, early Commando models, etc. But also necessary for States where a bayonet lug removal is required.
- All other rifle and carbine models had a Bayonet lug
* Note, there are actually two different styles of "Shaved Bayonet Lug":
- Our standard method, as shown in our pictures, is to remove the Lug completely. If ordered online, this is what we will deliver to you.
- The second method is to shave off only the wings of the Lug, leaving a center post still in place. This serves to make the Bayonet Lug inoperable, yet still looks like it is there. For this option you would need to ask for it in the "Notes" section of your order.. or call us after you order and request this change.