These are 5 mm. pin, clear plastic locking shelf pegs. Constructed from mold injected clear plastic. They feature self-locking tabs to prevent tilt-up on 5/8 thick shelves and keeping them secure in place. The pegs fit into 5 mm. holes in bookshelves or cabinets in your home or office. Each package contains 4 shelf support pegs. To install simply push the pin in the hole and gently place the 5/8 in. shelf in the locking area, to remove press the locking piece of plastic in to lift your shelf up.