Silicone-lined micro rings are fabricated with a aluminum metal. Interior of the ring is gentle on the hair with its protective, cushioned silicone lining, allowing you to install them flatter to the head for maximum comfort to the client, and allowing them to remain undetectable.It holds human hair very tightly after pinched and it will not easily get slide when wearing.There are two advantages for silicon rings:1) No damage to human hair. It is because there is very soft silicone lined inside, so it is very safe to human hair even it is pinched very tightly. 2) No silding from human hair.