Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Pump actually destroys presta valves!

I use this pump exclusively to fill up tubes with Presta valves. In the six months I've had it it has destroyed 6 tubes.The rubber part on the end is a tight fit over the Presta valve closure. Every once in a while, removing the Topeak (which takes a fair amount of force) rips the Presta valve closure from the valve, which means you need a new tube.Of course Schrader valves don't have this problem. Now that I've had experience with this pump breaking 3 different brands of tubes, I'm going to have to buy another brand.