Mack Tuff Cockswellers Black from Nasstoys of New York. 3 Silicone erection enhancers. Stay hard. Cum hard. Waterproof, non-vibrating cock rings. Phthalates free. Material 100% Silicone. Inner diameter size: small cock ring 1.25 inches, medium cock ring 1.375 inches, large cock ring 1.625 inches.