Our 21" Mower Blade is designed for use with our M18 FUEL™ 21" Self-Propelled Dual Battery Mower (2823-20). The 21" lawn mower blade is a direct replacement for the blade kitted with MILWAUKEE® M18 FUEL™ 21" Self-Propelled Dual Battery Mower. The steel blade offers you increased durability and longer life. The precision-machined cutting edge delivers an improved cut quality.