1.Box contents: 1 x 3speed bicycle gear and brake lever, 1 x 7speed bicycle gear and brake lever, 2 x brake cables (left and right), 2 x shift cables (left and right) 2.Brake and shift combination: integral construction for stability and easy operation 3.Visual Gear Shifter The gear shift is marked with 3 gears or 7 speeds, the optical gear position indicator ensures that the gear change is visible at a glance 4.Materials: combination of aluminium alloy and high quality plastic, waterproof and rustproof 5.Installation Instructions: 3 gears on the left side, 7 gears on the right side. Installation Detail Instruction: Shift cable is connected to the black cap, brake cable is connected to the silver cap 6.How to distinguish between front and rear trains? The front brake and shift cables are shorter and connect to the 3speed lever. The rear brake and shift cables are longer and connect to the 7speed lever. 7.Applications: suitable for MTB / city bike / road bike / folding bike. (NO EBIKE) 8.Note before purchase: this product (3 x 7 21 speed) is suitable for bicycles with 3 cranksets and 8 cassettes. 1 piece or 2 pieces cranksets are not suitable. 7 cassettes are also not suitable. Please check whether your bike is suitable before you buy