Schwalbe AV 21+ AP Air Plus Tube, 27.5/27.5" 54/70-584 IB AGV 40mm. Less air loss and less frequent pumping. Extremely reliable. Quality control for safe riding enjoyment. Due to the high proportion of pure butyl rubber, the Schwalbe Air Plus tube retains air significantly longer, requiring less frequent inflation. With its approximately 70% greater wall thickness, the Schwalbe Air Plus is particularly robust and offers above-average protection against punctures and impacts.