The 61mm 80a Butterballs offer the same shred-able formula that's become a fan favorite for so many riders over the years, but in a more compact package. The new 61mm size is now an ideal fit on your double kick, and perfect for just about any freeride situation. While it's the same urethane formula and Durometer as our 65mm and 70mm wheels, you might find a little better control and responsiveness with this smaller version of the Butterball. 61mm Diameter, 80a Durometer, 39mm Contact Patch. Butterballs Slide Formula, Round Lips for Smooth Slides over Cracks and Road Imperfections, Stoneground for Immediate Slides, Centerset Core.