Runs on 2 AA batteries. Newly designed hardware and firmware. Fits 2” and 1 1/2” openings on tank (includes removeable adaptor; remove adaptor to use on a 1 1/2” tank opening). When using outside, requires use of silicon cap (included) and Energizer Ultimate Lithium AA batteries (available in stores). BATTERIES NOT INCLUDED. NOT compatible with Roth 400 outside tanks or underground tanks.