What series Sandman are you talking about? 18V is Kingswood trim, and you could get seat inserts of a few kinds on Kingswood sedan but not on Kingswood utes or vans. Sandman was given Kingswood trim in HX and HZ but only had the base vehicle's trim in HQ and HJ, which meant HJ only had 18V on Kingswood ute Sandman.