any paint supply will have them. i don't pretend to be smarter than the folks that designed these guns. i use iwata guns and follow their advice . my paint booth is set up for hvlp. i shoot at 10 lbs and have no problems. many painters have bought these new guns but are having fits with them. fittings and regulators are a lot of the problem. my old binks reg/trap was pretty much useless under 20 lbs. iwata , sata and most other suppliers have useful q&a web sites with professionals to answer your questions. i would recommend going there with your paint questions. hub on the ASET web page is really helpful. he's known as Dr Gun
good luck.