Oregon 91-516 Mower Blade, 20-7/8" Center hole: 13/16" Requires 1, 91-516 blade and 1, 91-517 blade for 21" cut Enhanced mulching for bagging and discharge efficiency Stays sharp and durable for longer Replacement for major brand: Bolens Fits Honda models: Harmony Quada-Cut mower, Harmony II HRS