The outer material is drop plasto adhesive label, the inner material is made of ABS plastic. Product dimensions are stated as "inner and outer diameter". Inner diameter is 55mm, outer diameter is 58mm. The rim hub slot is suitable for rims of vehicles with an internal diameter of 5.5cm (55mm). The dimensions of the wheel hub may vary depending on the vehicle and the rim. To decide which wheel hub you should buy, measure the slot where the hub tabs fit from inside to inside. If the inner diameter measurement is within the inner and outer diameter dimensions specified in the product description, you can use it on your rim. Package Content: *4 pcs Wheel Hub Caps