These micro rings for hair extensions are a complete set you need for all your hair extension activities. It comes with silicone-lined aluminum micro links with a diameter of 5mm outside and 3mm inside. The silicone-lined micro rings are fabricated with an aluminum metal that delivers great results for even oily and hard-to-grip hair. It protects the hair and secures a fine hold. The interior of the ring is gentle on the hair with its protective, cushioned silicone lining that lets you flatter to the head for maximum comfort to the client.