Oregon 592-608 Mulching Blade, Gator G5, 21" Center hole: 9/16" Tungsten carbide is fused into the blade  creating an ultra-hard layer at the cutting edge and increasing the time between sharpening. X-Tended Cutting Length optimizes the cutting efficiency with each revolution. Gator Mulcher provides cleaner, more efficient cutting performance that can eliminate the need to bag, saving time and hassle. High-lift: The aggressive blade angle increases air flow to push debris up-and-out for superior bagging or side discharge. Replaces major brand: Everide