Z Clip Style Motor Retainer Set For Existing Airframes - includes 2 each Heavy Duty Z Clip, T-Nut Insert with grip tongs for press in insertion, Low Profile Hold down Screw. Z clips are strong steel 19mm (3/4″) wide. The center hole needs to be located at least 13mm (1/2″) from the edge to mount properly. Use on larger rockets to keep motors with thrust rings in securely during flight and ejection.