Bridgestone Battlecross X31 Soft-To Intermediate Rear Tire - 110/100-18 13851The Battlecross X31 is for a broader range of intermediate terrain in big bike sizes. Starting where the X30 left off, the X31 is enhanced with Bunker Groove technology which works by improving casing flex for enhanced traction in harder terrain and adds biting edges for traction in softer conditions. Rear tire Cooling Fins promote consistent traction and feel under continuous use (such as during a moto) by dispersing heat and minimizing inflation