These L.E.D. constant illumination Golf Ball sets a new standard in Night Golf Play. 4 Assorted colours per pack. Besides being official weight and size, the Night Flyer Constant On Golf Ball is a very sophisticated piece of equipment designed to light-up upon sensing a strong impact. Once activated, the built in computerised timer will keep the ball illuminated for 8-10 minutes after which the switch will automatically turn off the light to preserve battery life unless the ball receives another firm impact. Anytime the computer senses a strong impact the timer will be reset to zero and restart the 8-10 minute light-up period. Batteries in each ball are sealed and are NOT replaceable.