gb15 This gearbox is used for slashers with a 1.2 metre to 1.8 metre diameter cut. It has ratios of 1.5:1 and 1.93:1 and is capable of 75hp 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 shaft and gear are coupled by means of involute splines.