1) Prevent the screws from rusting. 2) , softness and toughness, not affected by climate. 3) No distortion and no problem under extreme temperature. 4) Easy to install, just the nut covers straight to the bolts. Product Specifications Manufacturer Part Number: 4F0601173A, 321601173A Interchange Part Number: 4F0 601 173A, 321 601 173A Other Part Number: 4F0 601 173 A, 321 601 173 A Diameter Size:17mm 25mm Style:Hexagon Compatible:for SEAT with 17mm Hexagon bolt,25mm Circle Bolt Colour:black gray Material:plastic Package Contents: 16 * 17mm Wheel lug bolt center nut caps 4 * 25mm Locking types caps Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.