4 Twin Shower DoorRollers (2pcs double top+ 2pcs double bottom ) Materials: Plastic, Main body bracket Zinc alloy , -bearing POM ABS brass axis - never rust Shower Cabins and Steam Cabin Enclosures Easy Glide Eeplacement Shower Door Roller From Picture Clearly see which Top /Bottom Roller Glass Open-Hole: 10MM-12MM can be fit Pulley: 23MM , GlassThickness: 4-6mm Suitable for most Shower Enclosures Shower Cabins and Steam Cabin Enclosures 2pcs double top+ 2pcs double bottom.