These rings replace your lost or damaged ones, so keep them on hand for fast replacements! Order by the diameter of your tow bar. This Rubber Ring has a 3-1/2" or 4" I.D. and fits most tow bars on the market with a 3-1/2" or 4" I.D. bottom bar. Sold individually. Two rings required per tow bar. 6" O.D. x 1-1/2"W.