Optional New Hardware Kit: UMI offers the option of new high grade mounting hardware for your classic Camaro or Firebird. 1970-1974 cars use ?? standard hardware on the lower a-arms while 1975-1981 use 14mm metric control arm hardware. UMI suggests checking your vehicles current hardware size before ordering to confirm. UMI a-arms are supplied with both sets of mounting sleeves to except either hardware sizes. Hardware kits are Grade 8 standard and Grade 10.9 metric with Ny-lock nuts.