Holt Allen's Fixed Spinnaker Pole Ring Bracket has a stainless steel curved base with a 2 in. (51mm) diameter. Both of the rings are 1/4 in. (6mm) thick and have an interior diameter of 9/16 in. (14mm) . Its curved base radius is 2 in. (51mm) to 2 3/4 in. (70mm).