These quarter turn fasteners provide positive locking in quick change applications where there are frequent insertion and removal of a fixture. They allow for consistent fastening force eliminating the chance for under or over tightening by the operator. The fastener is mounted to the fixture and the pin (sold separately) is mounted to the base. After placing the fastener on the pin, turning the knob one quarter turn locks the fastener into place with four balls. The fasteners are marked with "ON" and "OFF" indicators to show the position of the fastening pins. They can be used with locating pins to provide highly accurate positioning. The body is made from nickel-plated 1045 steel or 303 stainless. The knob is made from 300 stainless steel. The balls are made from 440C stainless steel. The spring is made from 304 stainless steel. The socket head cap screws for mounting are included.