Laserglow Technologies Galileo is the latest in functionality reliability and output power stability. The click-on click-off switch allows hands-free operation and easy use when continuous operation is required. The miniature heat sink means that the output will not drop during long operating periods and the single lithium battery will keep the unit running for up to 2 hours! The Galileo is ideal for alignment astronomy and all other continuous use applications that require a green laser beam with a 4.5-5.0mW power range.