Usually a vertically mounted device holding balls and feeding them into the marker. These can be gravity fed, agitating, belt feed, sound operated, etc. The main point about loaders is that if the marker can fire faster than the loader can provide balls, and the marker does not have a ball sensing "eye" to keep the bolt from going forward before a ball has dropped, there is a great risk of chopping paint. LPR: Low pressure regulator. Method of operating guns at lower than what is considered the standard tank output pressure. Lube: Almost always referring to applying grease to the o-rings of a marker. If, after cleaning one's marker, it leaks air, or does not hold its pressure, the o-rings or seals need more, or better lube (or there is a missing, damaged, or mis-installed o-ring or seal...markers are not high-tech-rockets). Mag: Slang term usually used to refer to the Air Gun Designs.