This document provides maintenance and repair instructions for Rider Pro 15, Rider ProFlex 18, and Rider ProFlex 21 ride-on lawn mowers. It includes specifications, diagrams, safety guidelines, and procedures for tasks like engine removal and replacement, transmission service, and mower deck maintenance. Technical details are provided for the Kawasaki engines, Tuff Torq transmissions, electrical systems, dimensions, weights, and other components.