Does sporting goods refill paintball tanks?

There are non refillable, disposable cartridges that range from the standard 12 grams to 4 oz. There are also small refillable 45 butt stock tanks and other small and long tanks like it. After 4 oz, a tank must be fitted with a "burst disk" which allows it to bleed out if over pressurized.

Any refillable tank over 2 inches in diameter needs to be hydro-tested every five years.