Magnets blade balancer. It balance any lawnmower blade with a hole in the middle. Replacement part number:339075B, 42-047 Made of high quality metal material,the thin metal rod to check the blades to see if they are bent,providing a smoother cut.When the blade is balanced, it be horizontal. Please make sure there is enough space on either side when you mount your balancer,so that blades can rotate 360 degrees without obstruction and do not to hit anything., Weight: 2.83734931194 pounds, Manufacturer: Tuidzljd