For Extra Thick results, look no further than the Doc Johnson’s OptiMale 40mm C-Ring! Made of soft, stretchable silicone for easy use around the shaft or testicles, these cock rings are perfectly suited for creating the most optimal of erections, and prolonging ejaculation. Phthalate-free. Inner diameter 1.7 inches, inner circumference 5.33 inches. Width/diameter 2.30 inches, circumference 7.20 inches.