OE Number 251390 Features RC-51H This gearbox features a Hydraulic Motor Mount with a 1:1.93 Speed Up gear ratio and a internal 1-1/4" 14 Spline for hydraulic motor, with a 2" 15 tapered spline output shaft for use on many Skid Steer rotary cutters. Each gearbox features high speed bearing units and heat treated gears and shafts to ensure long life. Has a Four bolt mounting matches industry standards, 4-3/4" on centers. Each gearbox includes blade carrier mounting nut and cotter pin. Gearboxes are shipped dry and require 80-90W gear lube or equivalent.