The AR243 arbor is used in conjunction with Aimshot .223 Laser Bore Sight. It is made of 100% brass for quality and durability. This arbor is used for all of the following calibers: - 243 Win, 308, 7mm-08, 260, 6mm, 7.62x54, .307 Win, 444 Marlin, 220 Jay bird, 22 Mark-2, .356, 7mm Shooting Times Easterner.