WTB Proterra Tough i30 Rear Wheel - 29" 12 x 148mm 6-Bolt BLK Micro Spline 32HWTB Proterra Tough i30 Rear Wheel 29" 12 x 148mm 6 Bolt Black Micro Spline 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