Colour 23mm. < ul >< li > YuanQian Set of 4 Twin Shower DoorRollers 23MM ( 2pcs top and 2pcs bottom ). < li > Glass Open - Hole : ¦ 8 - 13MM can be fit ; Pulley : 23MM GlassThickness : 4 - 6mm. From Picture Clearly see which Top / Bottom Roller.