I've got an Airzound. Given the nature of Shanghai traffic (chaotic at best) and the length of my commute (24km one way) I use up a full bottle of air on a one-way commute, so I have to fill it up again before I head home. While I wish the reservoir was a little larger, I still can't say enough good things about it - it's made many a motorist take notice of me, which is very difficult to do with Shanghai drivers, most of whom wouldn't even notice a bike if it was right in front of them.