The next-generation AR10-15 Combo Vise block comes equipped with a slot, designed specifically for Odin Works Lower Receiver Vise Block Inserts (sold separately). This indispensable tool needed for the assembly of an AR 10/15 upper. The ODIN Works Vise Block allows you to secure your upper while you clean or install barrels, forends, muzzle devices, and any accessories you want to mount on your upper.