gb20 These gearboxes are used for slashers with a diameter cut of up to 1.6 meters. The boxes have a ratio of 1.933:1 increasing and is capable of 45hp at 540rpm input. The blade mounting hub is fitted with a seal protector to help prevent grass, wire or any other objects from penetrating the oil seal. The input shaft and bevel gear are coupled together by means of involute splines.