These receivers are installed in the sub-plate or machine table to receive the locator units. Universal bolt-in receivers are interchangeable with competitive ball locking systems. They allow you to take advantage of the speed, precision and easy installation of the SpeedLoc System without the need to produce new sub-plates or reworking existing sub-plates. Mounting socket head cap screws are included. 180,000 psi tensile strength minimum. 140,000 psi yield strength minimum. Made from heat-treated 4340 steel with a black oxide finish.