No need to worry about batteries with these units.   we offer two versions Version 1 delivers  a powerful uv light at 395nm and only takes seconds to permanently set the gel..    Version 2 covers a wide variety of light frequencies from 365 to 405 nm, covering most of the band widths used in the uv setting gel market. (We have yet to find a gel that this unit will not set, but check the setting frequency of your gel prior to purchasing this lamp)).   Built with a swan neck and a strong spring loaded clamp it is easy to manouver.    The lamp should be clamped on a horizontal surface...  (Our Diamond Gel Coat sets at 395nm)