These are two mini CO2 regulators. They were both used for less than 4 months. They work well and I want to resell them instead of keeping them in a closet. I will ship them with two 20 oz CO2 tanks. This is the description from Amazon of the original product: Dual stage decompression,pressure adjustable. This aquarium co2 regulator is the triple stage design, very stable output pressure and CO2 flowrate, cylinder inner pressure reduced, flowrate will not change. Working pressure can be adjusted from 0-60 psi 12V DC solenoid with precision needle valve. This co2 regulator use 12V DC solenoid valve repalced AC solenoid valve, safer and more stable, lower power, no noise. Aquarium specific needle valve, High precision fine-tuning easy for co2 to be 1 bubble in 3 seconds Bubble counter. Together with bubble counter, you can read your co2 flow rate directly via the bubble counter. Bubble counter with check valve function, stop water backflow to bottle. Class 1 manufacturing technology. The co2 regulator is made of hard aluminum alloy, surface spraying treated. Pressure knob and fine tuning are very easy to adjust Mini size for almost all tanks. The regulator compatible with Painball tank, all size CGA320 threaded cylinder and 5/8'' UNF threaded disposable co2 cartridge.(Most 80-90g cartridges are 5/8'' UNF thread. Fluval 45g threaded 3/8'', NOT suitable)