The Topstar 6990 hard floor castors are the perfect replacement for many Topstar office chairs. Made of black plastic, they have a pin diameter of 11 mm and a pin length of 22 mm. The individual castors have a diameter of 65 mm and the overall diameter is 9 cm. With this castor set, you can quickly replace defective castors on your Topstar chair. The castors are particularly suitable for hard surfaces such as wood, parquet, tiles or stone.