bottle must be filled by nitrous LIQUID WEIGHT ONLY, bottle pressure means nothing. 2.5 bottle weighs 3.7 sitting on digital scales with feed line attached, fill to 6.2. now ur fill and pressure will be correct. u cannot fill a 2-2.5 bottle with it at room temp, needs to be frozen down to accept nitrous. i put mine in 0 degree freezer overnight, 5 minutes to nitrous station the bottle will literally suck in 2.5 lbs once flow valve opened, may have to pressure hammer it once of twice. warm bottle u have to force nitrous into, will not fill fully and bottle pressure high. filling bottle correctley is the key to a nitrous system.