Hub bolts are high-strength bolts that connect vehicles to the wheels. The connection location is the hub unit bearing of the wheel! Generally, class 10.9 is used for mini-cars, class 12.9 is used for medium- and large-sized vehicles! The structure of the hub bolt is generally a knurled key file and a threaded file! And a hat head! Most of the T-shaped head wheel bolts are above 8.8 grade, which bears the large torsion connection between the car wheel and the axle! Most of the double-headed wheel bolts are above grade 4.8, which bear the lighter torsion connection between the outer wheel hub shell and the tire.