A simple one way valve for "es2 pro" sprayer. Dumb thing loses it's prime normally, specially with alcohol, so I made it keep as much liquid in it. Makes it so much easier to reprime, use any form of suction on the sprayer, a syringe with a special tip works. Is just a snap fit, seems to work.... I know resin printing it is pretty much required I think.... Required Hardware4.5mm ball, standard bb size