This listing is for one replacement Howse Rotary Cutter Gearbox, 4 bolt mounting with bolt hole centers of 4-3/4" and 6-3/4" on a diagonal. This gearbox has a 1-3/8" diameter smooth input shaft with a 1/2" shear pin hole and a circlip groove at the tip. The output shaft is 2" (1.97") with 15 tapered splines. The box has what we call a square bolt pattern where the is no mounting hole directly under the input shaft, there is one hole to the left and right of the input shaft and again on the rear corners of the box forming a square mounting pattern when looking at it from the front or rear of the mower.
 
Box Specifications:
Heat Treated Precision Gears
High Speed Ball Bearings on Input Shaft, Tapered Roller Bearings on Output Shaft
1-3/8" Smooth Input with 1/2" Shear Pin Hole and Circlip Groove to Retain PTO Shaft
1.97" X 15 Tapered Spline Output Shaft
Includes Vent Plug, Cotter Pin and Circlip