We tested over a dozen different types of hot glue for our 3D coro and related projects and we've yet to find a better hot glue that doesn't turn yellow with UV exposure and that holds onto coro as well as our Ad Tech hot glue does. Sold by the stick (10" long) so you can purchase exactly the number you need. Each 10" stick is .44" (~7/16) in diameter (this is the most common size.) Can be also used to isolate and waterproof low voltage electrical connections.