The Prestaflator Mini is held in one hand while you push it onto the Presta valve Inflate and then pull it off. This leaves your other hand free to hold the bike! At no time do you need two hands for installation or operation. Prestacycles Quick-Click2 Presta head provides a good seal, yet is gentle on tire valves including tubeless and removable valve core products. Dial-in the pressure you want using the Regulator on your Air Compressor. Theres no guesswork and no over-filling when the Regulator pressure is set to your desired Tire pressure. Youll hear the air flowing into your tire for a few seconds, and when you dont hear it anymore youre done. The tire is at the exact pressure you pre-set. Inside the Prestaflator Mini is a 6061-T6 Alloy variable-rate flow valve weve engineered specifically for bicycle tires. The tool is so small it fits in your palm with your hand wrapped around it. Its easy to squeeze the trigger in your palm to make air flow faster or slower. Gentle air-flow for inflation or a powerful blast for seating tubeless tires.