Application Notes: The inner diameter of the sliding shower door plastic track is 1/2 inch, suitable for glass doors no thicker than 7/16 inch. If you are unsure of the glass door thickness, you can measure it with a caliper before placing an order. Material: Gray plastic structure, made of high-quality material, not easy to damage, long service life. Easy to Install: Shower door track rail. This glass shower door lower rail assembly keeps the shower door adequately aligned; no special tools or skills are required. A sliding shower door bathtub enclosure made of an extruded metal frame is very easy to install together. Good Friction and Wear Characteristics: This sliding shower door bottom rail plastic has a low static and dynamic coefficient of friction and is wear-resistant, helping to extend the guide's service life. Easy To Use: This is the best alternative to glass shower door rail components. It is easy to install, dampens vibrations, and has sound sound-dampening effects. It also runs quieter, making it ideal for showers in a calm environment.