WTB Proterra Tough i30 Front Wheel - 27.5" 15 x 110mm 6-Bolt Black 32HWTB Proterra Tough i30 Front Wheel 27. 5" 15 x 110mm 6 Bolt Black 32H. Proterra Tough i30 wheels keep the trail in check while everything else blurs by in the periphery. Reinforced by WTBs proven Dual I Beam support Proterra Tough rims feature a 30mm internal width to provide higher tire volume while also increasing sidewall support at lower pressures. Choose Proterra Tough when you need a wheel that wont let you down. Frequency Hub with top tier EZO