These nickel-plated steel O-rings can be used with many of our strap-on harnesses to accommodate a variety of dildo sizes. They also make an effective no-frills, utilitarian cock ring.
The number in the drop-down menu indicates the inside diameter. For example, Item A250 has an inside diameter of 1.25". (That's 1¼ inches.)
To find the diameter of a snug-fitting cock ring, measure the circumference around the cock and balls (at the base, behind the scrotum), and then divide by 3.1. Don't go smaller than that - you don't want to get stuck!)