The original Power Tank was based off of a 10 lb CO2 bottle and it is still our most popular size. It's compact enough to fit in most trail rigs, has enough volume for up to 35 in tires, and is light enough to easily walk it down to trail to fix a broken rig.
This is a good starter size bottle. The best part is, when you get bigger tires (it will happen eventually) or your air needs increase, everything simply transfers over to a 15 lb bottle, including the brackets. The 10 lb and 15 lb bottles have the same diameter so all of the components can be swapped right out.
Need more air but the 15 lb tank is too tall? A spare bottle system is perfect for folks that may be running larger tires but are also limited in space. Keep one full Power Tank set up in your rig. When that gets close to empty, swap over the regulator and handle to a filled backup waiting in your garage. Now, while the backup is being used, you have plenty of time to fill the first bottle. Easy.