The Chelsea 2P621 is a Chelsea 812KDA series gear designed for Mack applications. This is a direct Chelsea PTO component, sourced and sold by Pro Gear and Transmission. The 812KDA designation identifies this as a specific gear within the Chelsea 800 series PTO line, commonly used in Mack truck power takeoff installations. If you are working through a PTO repair or rebuild and need to confirm this gear fits your exact unit configuration, give us a call before ordering.FeaturesChelsea 812KDA series PTO gearPart number 2P621Designed for Mack truck PTO applicationsChelsea 800 series PTO componentSold by Pro Gear and Transmission