Jolly Logic AltimeterOne. Sold directly by the manufacturer, Jolly Logic For flying things like model rockets, planes, quadcopters, kites, and falconry (not hiking) Tiny: 0.57 x 0.71 x 1.93 (14.5 x 18 x 49mm) Weighs just 0.36 oz (9.9g) Recharges in any USB port