A Suspension ring is a strong polished metal ring about 15cm in diameter, designed to provide a tying point for rope based suspension bondage. It is attached to the overhead support (this could be a beam or eye bolt) by rope and then adjusted to a suitable height, usually slightly higher than head height. The large diameter of the ring makes it an excellent anchor for multiple lines and is much easier than trying to thread your lines through an eye bolt in the ceiling or a carabiner. The large opening also makes it easier to release your lines at the end of a session.
As well as simple rings, more complex designs are available. Prices range from £40 upwards.