RYOBI 21 in. Multi-Blade Replacements are the best solution for replacing your 40V Brushless Mower's dull or damaged blades. These blades are optimized for cordless mowers, improving cutting efficiency and increasing runtime. The Multi-Blades provide a superior cutting, bagging, and mulching performance with enhanced hardened steel durability. Buy with confidence knowing that this OEM part will work with your RYOBI 21 in. 40V Brushless Mowers. Replacement part for RY401150US and RY401200.