Power Module & Metal Slipper Upgrade Set: BOOST BOX ARRMA 3S 4S Red Full Metal Center Gearbox 57T+Motor Gear Assembly 10-Piece Set with Flat Head Hex 414MM 1P, Cup Head Hex 310MM 2P, Pan Head Hex 2.56MM 2P, M44 Machine Screws 3P, M3*3 Machine Screws 3P, 0.8mm Pitch 3.175mm Hole 15T, 17T, 20T Each 1P, 5MM Hole 15T, 17T, 20T Each 1P.

Full Metal Motor Seat Center Gearbox Housing. It has a more attractive appearance, provides better heat dissipation for the motor gears, is less prone to deformation, and makes the gear motor more durable. It comes with a 57T chrome steel large gear inside.