Quoted: yes different will work, Bravo Company has the best price for a front sight with bayo lug.  Marked F for use with flattops...

Thanks Quake_Guy!

. . . in stock

Quoted: Quoted: Quoted: yes different will work, Bravo Company has the best price for a front sight with bayo lug.  Marked F for use with flattops... Thanks Quake_Guy! . . . in stock So should he get th 'F' model or the standard model?  I know Colt have different FSB for their flattops, but Bushmaster uses one standard.  If he get's an 'F' model, it will mess up his rear iron sight, no?

The 'F' FSB is milspec for flat top rifles and carbines.  Most commercial manufacturers (except Colt and LMT) use the A2 FSB on their flat top uppers.  Sometimes there will be zeroing problems with a milspec BUIS.  Commercial manufactures will use shorter carry handles and shorter flat tops to make the adjustment of the shorter A2 FSB.  It can get confusing. . . .
My best suggestion is to use a milspec BUIS and try to get a zero; if you can - then replace the FSB with the standard A2 (your flat top upper is made shorter).  If you can not get a zero until the FSP is backed almost all the way out you have a milspec upper and should use the F-FSB.

Milspec BUIS are: Colt carry handles, ARMS, LaRue, MI, LMT, GG&G, KAC, Troy and some others.