Using these No - Foil Flat Back SS16 Rainbow Crystals is easy. First, if you want to jazz up your Circuit Playground Express or an e - textiles project, take a small amount of glue. Then, carefully place the glue right over the opening of a NeoPixel and stick a crystal on it. It'll add a nice sparkle. As for the note, since there's no foil on these crystals, you won't get the extra shimmer that foil usually provides. When it comes to maintenance, be gentle with them. If they get dirty, you can use a soft, dry cloth to wipe them clean. Also, keep them in a dry place. And don't worry too much if you accidentally drop some on the floor because you have 100 in the pack.