RaceFace Era SL Rear Wheel - 29" 12 x 148mm 6-Bolt Micro Spline Carbon BlackRaceFace Era SL Rear Wheel 29" 12 x 148mm 6 Bolt Micro Spline Carbon Black. Ride Light. Log Miles. Get Loose. The Era SL wheel was designed to bridge two riding disciplines with the goal of excelling at both ends of the spectrum. Not your typical XC race wheel nor a strength forward Enduro wheel. A happy medium designed specifically for the mass of riders who sit happily in between. At 385 grams the Era SL rim is the lightest ever produced by Race