I am building a super lightweight AR-15 and am looking for a flip up front sight sight gas block that will fit on .625" diameter lightweight barrels. My requirements are 1) Must be pinned, none of that clamped nonsense 2) No UTG/CAA/other airsoft junk. I don't mind paying the prices for vltor or gg&g. This would be ideal but it only comes in a .750" diameter version: