The Mulching Blade is a heavy-duty lower blade that turns grass into fine fragments. The lower, Mulching Blade is interchangeable with the High Lift Bagging Blade and the Extended Run Time Blade. The Upper Blade is the 2nd blade of the multi-blade system and is included in this set. This blade slices the grass the lower blade sucks up to enhance the cutting performance. This all steel blade is specifically designed for the all EGO POWER+ Select Cut™ 21" Lawn Mowers. The EGO Select Cut™ Multi-Blade System is EGO‚s solution to replacing premium gas lawn mowers for good. EGO parts are designed specifically for your EGO POWER+ Lawn Mower and offer the highest quality, performance and value. (Nuts and bolts not included.)