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: 1.7â , Inner Circumference: 5.33â . Width/diameter: 2.30â . Circumference: 7.20â .