Replacement Lawn Mower Blade The PAC001478 is a replacement 21" lawn mower blade designed for the HYM530SPER Hyundai Petrol Lawn Mower. This blade features a large cutting edge and curved surfaces to cut grass into very fine, smaller pieces before it falls back to the lawn for greener and healthier grass. Length: 520mm / Side Hole Square 16mm / Side Hole Oval 20mm / Thickness: 50mm / Distance Between Side Holes: 220mm / Width: 50mm. Quality, HYUNDAI Genuine Replacement Blade.