i also have the lhp400, i have all 3 caps. supposedly the purple cap is meant for difficult metallics but i honestly couldnt tell a different between that and the orange cap. i also have a dv1 , and i can honestly say,, that the gun does all the work. it makes spraying metallics very easy and without effort. but, also have to be consistent with overlap and distance, but if anyone already has that part established, then the dv1 makes the job much easier.