Definitions by Psi Sushi

o-ring 

A circular metal ring for something to clip onto or fasten to.

The collar had an o-ring for a leash

o-ring by Psi Sushi November 8, 2003

d-ring 

A D-shaped ring, the flat section attached to a collar/cuff/belt/other surface for the purpose of fastening something to that surface.

The cuffs were clipped together with d-rings

d-ring by Psi Sushi November 8, 2003