The ring is strapped over the hard penis and the cuff is tightened. Double model: please pull additionally the second loop over the testicles and the lower cuff is tightened strong so there is no pain (tighten by feel - risk of congestion of the veins). Caution: You should tighten the cuff carefully so that the skin is not pinched. Features: black rubber round cord made of NBR - elastomer (nitrile). High strength and elasticity. Food-safe. The noble cuff is made of hard-aluminum and treated with an anodized color. There is no risk of skin allergies during wearing.