Not that bright, but light lasts a long long time!
These were fine. It frustrates me that in the pictures they make it look like the whole balloon lights up, but in reality its a little 1"ish light inside the balloon and it's mostly only bright at that point. It KIND OF illuminates the rest of the balloon. That being said, the lights remained functional for weeks, and the balloons were nice quality. We used them for play for at least a month past the party we bought them for.
Rating: 3 stars