High Strength Acrylic Solvent Cementable Polycarbonate Cam and Internal Parts 90 Rotation Tubular Key Labour Saving All internal parts are made with polycarbonate for superior strength, and a high strength acrylic housing for easy solvent cementing. The Double D shaped housing fits a standard cam lock hole. When a round hole is used the flat side of the cam lock can be used to ensure proper alignment. Solvent bonding stops cracking problems caused by an over tightened mounting nut, and a solvent bonded lock won't turn when installed in a round hole. Try one on your next display.