Thats on the inline reg, basically you get the output pressure from the bottle - passes into the inline this knocks it down to (200psi (not sure what pmr's run at??) presumably by the use of faries/gnome's or other small industrious creatures) the air then goes through other air paths (can you tell I don't quite know the airpath on the PMR?) but basically theres some faries and stuff, magic happens, just read the manual and you'll be fine