That type of tank will work for air rifles. The 4500 PSI SCBA tanks need a different fitting (fire house type) at the valve. You need to find out if where you can get tanks filled can fill to 4500 PSI, otherwise the carbon fiber tanks are not worth the extra money. Also, looking at the add for the used tank on the link you added, it appears those are pretty old tanks. Does it include a current hydro? Also, CF tanks have a fixed life, 15 years, I think. Beyond that service life, certified fill stations will no longer fill them, regardless of condition.