Thinking about becoming single? It's great for weight loss, easier maintenance, and for looking faster. Rotor wanted to craft a 1x crank for mtb frames with 24 mm axles that could be matched with the QX rings (or noQX rings – your choice) for optimum pedaling efficiency with a single chainring setup. Crank arms CNC-machined from 7075 aluminum are combined with proprietary technologies to yield cranks with an exceptional stiffness-to-weight ratio that can handle an off-road thrashing. Together with Rotor's Universal Bottom Bracket (UBB) system, the REX 3.1 offers a performance upgrade opportunity for all single ring mountain bikes with 24 mm frame axles.