Cobalt is a bold and strong color that is great for this 4mm diameter finished necklace of neoprene rubber. Beaders like neoprene because unlike natural rubber, it does not burn or tarnish silver. For this reason our necklace has a .925 sterling silver lobster clasp. This also means you are free to use sterling silver bails, charms or beads with links! At Artbeads.com, we like to keep the sky the limit, just for you! The neoprene rubber material is latex-free, so it's safe for anyone to wear!