U-bolts attached your leaf springs to the axle and as such are very important from a safety perspective. In fact, so much so, that it is considered mandatory to replace the U-bolts whenever leaf springs are separated from the axle assembly.
Usually we use U-bolts from Carrolls Suspension in Brisbane who are a major long standing spring manufacturer who offer U-Bolts manufactured from durable and strengthened product made of high-quality material, to generate a long life. All U Bolts are supplied with longer nuts for improved torque-down strength.
After fitting U--bolts, its also critical to tighten them 1000 km after they are fitted and you will be quite amazed at how much they will tighten up.