These pumps are often used by mountain bike or road bike racers who need to save weight, and time if they get a puncture during a race. They can be a one time use pump - or a re-usable pump with the purchase of another cartridge. Because they use CO2, some of the pumps may be expensive. Most use standard threaded 16g CO2 canisters, originally designed for soda water fountains. They offer a super fast inflate to save you valuable time and energy (great for winter use when you fingers are getting cold and stiff).