Jim, I installed dual Buel air horns earlier in the year. I replaced the 20 year old single that sounded more like a large dieing mammel than a horn. I used the existing CO2 bottle/regulator system and it works great. I removed the tank and had it checked and refilled at a welding supply store. It will be interesting to see how long one bottle will last. I have the regulator set at about 60 psi. You will need a solenoid for the horn button as well. Robin Goffrier Amazing Grace '81 50' O/A Pilothouse Portland, Oregon