According to scubagaskets.com, the o-ring size for the Geo 2.0 is 27mm inside diameter with a 1.3 mm cross section and 70 hardness nitrile. This should also be the same size for similar computers such as the Oceanic F10, Atom , Bud, Aeris Manta, Epic, Tusa Talis, Aqua Lung i200 and other similar...