I’ve carried and used these for years now, they clean up lenses to as new without scratching or using chemicals. They can be washed and after 15 years of use mine is as good as the day I bought it. I picked up a secondhand 135 f3.5 MF lens once for a bargain as it had a marked element. But after wiping it clean a couple of times with the cloth the lens was perfect and gave me several years of excellent service until I finally traded it in to the same shop making a 50% profit in the process.