I bought the small size from backcountry a few weeks ago on a killer 50% off deal. I wanted a compact, reliable pump as a backup to CO2. I used it for the first time last weekend on the trail. I came across someone trying to add air to their tire. Her pump was broken, so we used this one. No problems at all. It takes up minimal space in a hydration pack & works on Presta & Schrader valves.