Jabsco 4-Blade Chopper Kit w/Lock Nut f/18590 Series Macerator Pumps4 Blade Chopper Kit with Lock Nut for 18590 Series Macerator Pumps The Jabsco 4 Blade Chopper Kit replaces a worn, broken, or malfunctioning macerator chopper in the 18590 Series. The chopper is designed with 4 heads, each with its own blade to break up large debris before it enters the pump and other fluid lines. Includes a lock nut to secure it in place.