The hour just before sunup can be the best bite of the day for sunfish. The big bluegills come into the shallows to feed. Casting a slip bobber set to hold the bait just off the bottom is a sure way to catch a batch of feisty fish. Unfortunately the slip bobber can be hard to see in the dim dawn light.
Thill tried to remedy the problem with a lighted bobber. Their first attempt was not too successful. The bobber was larger than optimum and used a non-replaceable battery. The pricey bobber became useless after about 12 hours of being lighted.
Their second attempt is much better. It is a trim four inch slip bobber with performance which is almost as good as their premium balsa floats.
The top of the bobber screws off to replace the battery and bulb assembly.
The heart of the bobber is a clever light/battery assembly only 3/16 inch in diameter by 1-1/2 inches long. The bulb is turned on by pressing down on it until it lights. It is turned off by pulling the bulb out slightly.The battery lasts about 20 hours. The bulb comes in three colors so multiple bobbers can be used at the same time.
The bobber is about right for a #3 split shot, and is very sensitive. The only downside is cost. The bobbers sell for around $7.50 and a replacement battery/light is about half that. You can probably beat those prices by shopping around.