The CMC Picatinny Rail Cover, Lo-Profile covers 18 slots. The cover Eliminates the sharp edges on your Picatinny quad rail forearme and protects the rails from damage. Covers easily snap on and off and can be configured to suit the users needs and form a very low profile grip. Covers are made from Santoprene and give a rubbery surface and can easily be shortened to custom fit your specific application.