Carlisle Ultimax Pro Drive Belt - 1-33/64in. x 44-7/16in. 140-4352U4 In the quest of creating the best possible belts for snowmobiles, the Ultimax 3 has evolved into the new Ultimax Pro. The new Pro belt features a thicker cross section so more surface area contacts the clutch. This means less slippage over a broader speed range for quicker acceleration. The new cog design dissipates more heat and maintains flexibility. Cooler running belts mean longer lasting belts and better performance for your snowmobile.