Package Contents: 504 sanding bands, 24 sanding drum mandrels, 2 self-tightening mandrels and 1 combination wrench, total 531 pieces in 1 set. Essential Accessory 7 Grits: These sanding brands contain 6 sanding grits (80, 120, 150, 240, 320, 400, 600 grits) and 3 diameters (1/2", 3/8" and 1/4"). Each grit and size has 24 sanding bands for you to use and replace. Universal Drum Mandrels: 24 reusable drum mandrels contain 3 diameters: 1/2", 3/8" and 1/4", 8 pieces for each size. Common and standard size suitable for all rotary tools like Dremel, etc. Easy to install - make sure the drum has been screwed on tightly, drum mandrels with self-expanding rubber cushion, which makes the sanding bands close to the mandrel firmly and achieves a better finish; Note: Please wear professional safety glasses to protect your eyes, as grit may fly when the sanding drum rotates at high speed. Wide Compatibility: Standard and full-size drum sander set, widely used for smoothing curved surfaces and