This clamp on drink holder easily attaches to a bed rail, wheelchair, walker or bike to allow for easy access of a drink. Clamp adjusts to mount on a horizontal or vertical rail with a diameter as small as 3/4" and as large as 1 3/4". No drilling needed. Easy to clamp on and off. The arms that hold cups and bottles have some flexibility and can accommodate containers up to about 2 3/4" in diameter. Bottles or cups up to 2 1/2" in diameter can easily slide in and out without spreading the holder's arms open. This is a helpful way to improve fluid intake and promote independence.