Rotary 12963 PK3 Copperhead Mulching Blades Replaces: MTD 742-0677A, 942-0677 Fits: MTD RZT Series, Z6600 17ARCACK099, 1500 Tractors, 17AF2ACK099, 17AF2ACK099; Troy Bilt 17ARCACK011 Length 18-1/2"; Width 3"; Center Hole "Star" Pattern; Thickness .204"; Set of 3 Heavy Duty version of 11719. Requires (3) blades to fit a 54" cut