Universal stem size - roll diameter: 50 mm, pin diameter: 11 mm. The 360 degree rotatable roll enables easy rotation and smooth movement of the devices. Safe for all floors - The soft treads are made of durable polyurethane, which is very resistant to chemical and mechanical influences. Scratch-resistant and anti-abrasive - rollers are durable, maintenance-free and problem-free. Treads coated with high-quality polyurethane, offers very high protection against scratches and abrasion marks. Easy to Install - No Tools Required. Pull the old rollers out of the pivot in the swivel chair frame and simply click the replacement rollers into the thread with the pin. Universally applicable - These stylish premium office chair castors are suitable for all floors made of hardwood, carpet, tiles, laminate, parquet, vinyl, PVC, concrete, linoleum or natural stone. Color: Black + White Pin diameter: 11 mm Roll diameter: 50 mm Shaft length: approx. 21 mm Attention: Please absolutely Check the correct pin diameter before ordering Scope of delivery: 5 x swivel chair castors