Operate metal halide or high pressure sodium grow lights with this state-of-the-art digital ballast from Galaxy! The Galaxy Select-A-Watt digital ballast is manufactured to provide today's serious grower with maximum flexibility and performance. The ballast properly drives a 400- or 600-watt lamp to ANSI specifications. Set the switch to the desired wattage, insert a lamp of the same wattage, and the ballast operates that lamp. To reduce in-rush current spikes, the ballast delays 1-3 seconds each time it starts, using its pre-programmed digital random start feature. This ballast includes a 6-foot, 120-volt power cord. A 240-volt power cord is sold separately. For dimmability, use a lamp with a wattage higher than the specified wattage on the ballast.