SRAM Eagle 90 Ebike Crankarm – 170mm ISIS Brose Cap Black. The Eagle 90 Transmission E-MTB crank is a sleek sturdy answer to a growing demand for robust and aesthetically pleasing components. This unique design is forged from aluminum for robustness and dependability without compromising weight. Select E-MTB motors pair with our GapCap for an aesthetically pleasing integrated look.