Pinion gear using the coupler can convert 32P 48P Mod1 5mm pinion apertures to 3.175mm.so this product for motors with 3.175mm shaft diameter 550 540 3650 etc series motors.Makes 5mm pinion gear work on a 3.175mm (1/8 inch) shaft motor 3.175mm gear shaft adapter can be used to convert 1/8 pinion Gears motor to 1/10 pinion Gears motor, for 1/10 RC Scale Car Boat Redcat ARRMA AXIAL Pinion Reducer Sleeve Inner Dia.: 3.175mm(1/8 inch), Out Dia.: 5mm, Length: 12mm,Made of Steel more . Material:steel colour:silver Package Contents: 3 * Shaft Adapter 3 * Set Screw 1 * Hex wrench Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.