Use for T-REX 800E/700E/600E PRO. Motor Slant Thread pinion gear 13T x 1 M4 set screw x 2(M4x4mm) Brand new M1 motor helical pinion with Stainless steel material. This high strength and high rigidity characteristics can help to increase wear resistance and longevity. 800E Must with CNC Slant Thread Main Drive Gear/110T(H80G002XXW). 700E Must with CNC Slant Thread Main Drive Gear/112T(H70G002XXW). 600 PRO Must with CNC Slant Thread Main Drive Gear/112T(H60G001XXW).