Doc Johnson Novelties Optimale Men's Sexual Health and Wellness line. Optimize your experience with these silicone cock rings. The Optimale Thick C-Ring Set offers enhanced size and girth with three rings in 40mm 45mm and 50mm diameters. These rings are ultra stretchable for easy use around the shaft or testicles maintaining those long-lasting erections you have always dreamed of and prolonging your ejaculation. Video. 18.