Window opening : 12 mm adjustable ; Pulley : 23 mm : glass thickness : 4 - 6 mm. Compatible with most shower enclosures and cabins. < li > Electroplated Door Rollers : 23mm ( dia ) wheel top bottom shower door rollers, plated surface, rustproof ; fit for thickness of 4 - 6mm glass door, glass open - hole of 12 - 14mm.