This is a 21-inch 3-in-1 lawn mower blade (factory model 2105200317A), compatible with OEM part numbers 742-04100 / 942-04100. Made of durable steel with a black anti-rust coating, it features a 3-hole mounting pattern that fits most 21-inch deck MTD, Troy-Bilt and Craftsman walk-behind mowers. Designed for mulching, bagging and side discharge, it delivers a clean, even cut for residential lawn maintenance.