XS Sights XS Sights, Tritium Stripe Front Post, Fits AR-15 A2 Front Housing Sight, Installation Tool Included AR-2001-6 XS Tritium stripe front sight for the AR features precision machined stress proof steel" a vertical tritium vial" and white outline to provide front sight visibility in any lighting condition. 0.105" square top post. Each full rotation of front sight gives a 5" shift at 100 yards. Made in the USA. Fits AR front sight housing with front sight detent at 3" 6" or 9 o'clock.