DIMENSION: The white curtain hook has a length of 18mm, bottom diameter 9mm, a cylinder diameter of 3.2mm, and a spacing of 3mm between the top and bottom. COMPATIBILITY: Curtain Track Rollers fit for 9mm Wide Curtain Track Rail. MATERIAL: The track curtain hooks are made of high quality plastic. These curtain rail gliders won't stain your curtains due to rust compare to metal ones. EASY TO USE: This white plastic curtain hook is very convenient to install and use. You only need to insert several hooks into the curtain track at one end, and hang the curtain at the other end, so that the curtain can slide smoothly on the track, which is convenient and fast. SWIPE EASILY: Each curtain rail hook is specially designed to ensure an easy transition from track to track. The curtain gliders are high quality and offer effortless gliding through the curtain track sets. They make curtain opening and closing off more easily.