Heavy duty, machined aluminum vise block lets you clamp an AR-15/M16 upper receiver in a bench vise without risk of marring the finish or distorting the receiver from over-tightening. Dual-use design allows the receiver to be positioned top side up or, if it's a flattop, upside down; either way, the vise grasps the block and never touches the receiver. One side of the block fits in the underside of the receiver and is held securely in place with two, steel, T-pins inserted through the takedown pin holes, so you can install optics, perform thorough cleaning, and do other work on the exterior. Or, slide a flattop receiver rail into the grooves on the other side of the block and tighten t Mfg: Precision Reflex SPECS: Body - Aluminum, hardcoat anodized, matte black. 7" (17.8cm) long, 1A 1/4" (3.2cm) wide, 1A 1/4" high. Pins - Steel, black oxide finish. Fits AR-15/M16/M4 and clones with .250" diameter takedown pin holes.