Think it depends on what you are using them for. I know that Zaino recommends certain brands for cotton towels because of the possibility of poly threads in the towel. Even if they are 100%, you still need to check where they are manfactured as some countries may use polyester in the seams, but still call the towel 100% cotton. I think the shop towels from Costco may be labeled 100% cotton, but I wouldn't use them on paint. I think those are from Pakistan.