One input shaft for a Servis Rhino gearboxes used on SE15 mowers and several others ! Fits center divider box with a down shaft on a three gearbox 15' batwing mower. 1-3/4" X 20 splines at the PTO shaft,  19 splines where both the front and rear gears ride. This shaft measures about 14 inches overall. 
Shaft Specifications: 
14" Overall length
1-3/4" diameter with 20 splines at PTO
19 straight splines where front gear sits with 50mm diameter
19 straight splines where rear gear sits with 50mm diameter
49.9mm where both bearings mount
OEM part