Ring O's by Screaming O is the most effective toy that is designed to enhance your erections and provide more satisfying sex for both you and your partner.  The diameter of the product (from edge to edge) is 1.38 inches and the diameter of the opening is 0.75 inches.  The stretchy, comfortable ring stretches to 3 times its size.  It fits snuggly around the shaft's base of the penis.  This ring can be worn during masturbation or sex.