Engages the valve and works perfectly the first time every time.
Cons: It gets REALLY cold..wear gloves.
It's so small it's easy to lose it.
Recommendation: I have tried several mini pumps and another Co2 inflator, The pumps were all terrible, and the Co2 inflator was fine but it got recalled for a manufacturing flaw. It also the type looks like a pump and the cartridge goes inside it. This one is tiny and works every bit as good.
I carry this, and one Co2 cartridge or two, depending on the length of the ride.