These heavy-duty fasteners provide positive locking in quick change applications where there is frequent insertion and removal of a fixture. They allow for consistent fastening force eliminating the chance for under or over tightening by the operator. They are designed to be used with QCPCS-series clamping pins (sold separately). The fastener is mounted to the fixture and the pin 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. Turning the knob to the “OFF” position releases the balls and allows the fastener to be removed. For plates thinner than 6mm, a QCASP spacer is required (sold separately). The body is made from 303 stainless. The knob is made from 300 stainless steel or black plastic. The balls are made from 440C stainless steel. The spring is made from 304 stainless steel. Three socket head cap screws for mounting are included.