I had an old piece of furniture that needed to be refinished. After reading the reviews both positive and negative I decided to take a chance and give three different grades a try. The 80, 120, and 220 were chosen to get into some smaller trim work on the 120 year old walnut. Oh my lord what a mistake that was. I tried the yellow after watching some videos and choosing the speed included in the enclosed instructions of 4000 RPM for wood. A gummy bear on the end of a drill bit would have held up better and had more abrasive action.First the aggregate content of the material was nonexistent. After close inspection with a 10 power magnification it is my opinion all three grades are nothing more than the same quality, different colored rubber like material. All three grades in my opinion appear to be the same type of material, just different color. No difference in abrasive quality. In fact no abrasive quality at all other than what you would get with any piece of soft generic plastic.Second is the durability of the units. Within literally 60 seconds pieces were flying off at warp speed. Even when it was just free spinning and not touching anything it just flew apart and disintegrated. Applying it to the wood caused it to literally melt into flinders. This was at 4000 rpm. The enclosed instructions claimed the things were rated up to 25,000 rpm. What bizarro world was that technical writer from, that came to that design limit specification. If I had not been wearing a face shield I might now be blind. In one of the photos you can see some of the pieces on the work bench surface.Third and last but most importantly it actually melted and impregnated the rubber into the grain of the wood. Please look at the photos. It not only failed to remove any appreciable surface stain but actually made the job much harder. I had to go back and hand sand out the haze of melted rubber that was bonded with the wood. Small globs were easy to scrape off, but it actually stained the wood the color of the rubber so deep it took hours to remove. After using several of the yellow 80 grit and experiencing this horrible result I did not proceed with the finer grits for fear it would damage the wood even more.Please heed this and other negative reviews. You will see quite a pattern of performance complaints. I'm not saying the overseas origin of said product is the cause, what I am pointedly stating is that this is a horrible product. It does not perform anywhere near the stated claims and is actually quite dangerous to use. I don't know if the actual name brand 3M products work any better but I intend on finding out. They might be just as bad or actually work as claimed.Thank you Amazon for providing an easy no hassle return process which went off without a hitch. Perhaps there should be some system in place to check quality and performance claims of many products that receive a certain number of negative reviews. As it is you take a chance with all the loaded reviews making a product look better than it actually is.