Learn how to refile your Butane / Propane Mix Fuel pack stove canisters to save money. Much cheaper compressed propane canisters can be found in discount stores but with different style connections. The EN417 specification stove connection size that Campingaz , MSR, JetBoil and Colman use for pack stoves tend to be much more pricey.
This video will walk you through the steps to transfer compressed propane into a used up pack stove tank. Please follow his steps closely as to not put yourself into danger by over filling a gas canister. I have made a similar adapter myself that works great but he has filmed a good video that will help much better than me describing it to you.