Sprenger ULTRA Fit Comfort Roller Spurs in Stainless Steel / Brass 35mm. The Sprenger ULTRA Fit Comfort Roller Spurs are designed to sit perfectly and elegantly on your riding boot. The unique fit eliminates pressure on the rider's ankle and movement too to ensure excellent spur performance and to protect your leather boots. The Comfort Roller Spur features a 1. 375 inch neck with a 35mm rowel that sits horizontally on the spur, this is a unique design that provides a softer but more direct contact with the horse's flanks. Read more… The rolling action of the chunky brass rowel ensures a much softer feel for the horse due to it's rolling action on the horse.