At last a genuine addition to the fast valve armoury. DW4930 is designed to prevent wear and does this strikingly well. I don't think it helped on the absolutely brand new JP171SWS Cornet JP supplied it with because it seemed to be inhibiting necessary wearing in, but I'm certain that it combines added wear protection with a proper fast action on my older valve instruments. This is not the thinnest fastest oil - other brands are available if you want that, and it will still evaporate a bit if the instrument is not played for a long time - better to use Paxman spindle oil and loosen the top and bottom caps if you are laying up an instrument, but remember to oil well with proper piston valve oil and tighten the caps when you start to play it again!