The cartridges are used with adaptors to inflate tyres. They're great for road rides, or xc/endurance racing where you might not want to carry a pump...or waste time using one. The cartridges will inflate your tyre within seconds but the smaller cartridges are only really useful for tyres up to 2", anything above that you need two...which is where these come in as they're significantly larger and ideal for 2.3-2.5" tyres.