Roller material: plastic nylon material Roller wheel diameter: 25 mm& ÉWheel thickness for ; rollers: 5 mm For adjustment; maximum glass thickness: 4-6mm & for adjustment The minimum size of the hole in the glass is 10mm. DIY replacement: It is easy and convenient to replace this doorknob by yourself. You can simply repair it using a screwdriver and replace it with new rollers on the glass doors. Package includes: 4 rollers single wheel (2 upper single rollers and 2 lower single rollers and 4 caps).