This mount was designed for use with the Williams FP-GR TK peep sight. The corresponding front sight and block from Williams are: Lyman Globe Front Sight Williams Rear Sight Top of the receiver to the top of the rear sight dovetail is .330" Top of the receiver to the top of the picatinny rail is .45" This rail is ambidextrous. This mount is milled on both sides for bolt clearance on left or right handed models. Picatinny cross slots run the full length of the rail, which gives the shooter flexibility when mounting scope rings and other accessories. The channel in the center reduces the overall mass of the mount. Also, in many cases, it w Mfg: Egw