Sun Ringle Duroc SD37 Rim - 27.5" Disc Black 32HSun Ringle Duroc SD37 Rim 27. 5" Disc Black 32H. Rim strength comes from the careful combination of bead hook width sidewall thickness and spoke bed thickness. Whether youre on the race track or at the top of a questionable descent lowering your tire pressure to compensate for technical terrain control can require additional rim armor where it counts to make it through the day. Duroc SD is the solution for racers freeriders and everyone in between.