Small, efficient, reliable-the three key features of the Air Tool MTB Mini pump. With the inverted dual chamber design, this pump moves 20% more air per stroke than the unit it replaced, yet is 10% smaller. Inverted dual chamber design is smaller yet moves 20% more air per stroke when compared to our previous design, reducing pumping time by up to two minutes. Twist locking head is easily converted to fit Presta or Schrader valves. Machined outer barrel for extra grip while pumping. Aluminum inner and outer chamber for durable performance. Water bottle boss frame mounting bracket included. Max pressure: 60 PSI (4.1bar) Volume-per-stroke: 55cc