PRODUCT DESCRIPTION Oregon Lawn Mower Blades 91-183 Ferris/Ariens/Gravely The 16-1/4″ Oregon lawn mower blade, part number 91-183, is manufactured to precise OEM specifications for optimum performance. Three blades are required to mow 48 inches. Can be used as an alternative to Ariens/Gravely part number 04919100, Ferris part numbers 20843, 20843S, 5020843, 5020843S, 5020843X2 and Giant Vac part numbers 21537, 3021537, 3021584. Length 16-1/4 in. Center hole 5/8 in. Width 2-1/2 in. Thickness .250 in. Air lift 1 in. Three blades required to mow 48 in.