The 742P05643 lawn mower blade is a precision-manufactured replacement part that directly replaces 742-05643, featuring a direct-fit 21 inch S mount design that enables seamless installation without modifications for all matching lawn mower cutting deck models. Constructed with premium high-carbon steel material and a precision sharpened cutting edge, this blade delivers superior clean and even cutting performance for all grass types, effectively trimming lawn turf with minimal tearing to maintain a neat and healthy lawn appearance. It is engineered with a thickened steel core for enhanced structural strength and impact resistance to withstand rocks, debris and uneven lawn terrain, preventing blade bending, dulling and premature wear during frequent use, and the durable anti-rust coated finish resists corrosion and grass clipping buildup from outdoor moisture exposure for long-lasting sharpness and reliable cutting function. The exact S mount dimensional matching ensures a tight secure fit with cutting deck spindle components to avoid wobble, vibration and uneven cutting, and the balanced blade design optimizes smooth mower operation and reduces strain on internal drive systems. Built to meet strict cutting and fit standards for lawn mower blade applications, it is recommended to refer to the original equipment owner's manual to confirm proper fit and installation guidelines for your specific machine.