Top cover bolt for holding the top cover on *Lucas DPA style pump. PLEASE NOTE: All suppliers of this screw have went to a metric version of the screw, even OEM*. We order the standard and we get a metric. If yours was a standard it will be tight going in, however, it has worked is all that we have tried it in. I just want to make sure you are aware of this. If yours came out with a 3/8" wrench then these will be tight going in using a 10mm wrench, same acorn nut will also work.