Kurt Kinetic's 12mm Traxle Through-Axle lets you attach your mountain bike to a Kinetic trainer without changing the original skewer. The Kinetic Traxle comes in 3 thread pitches: - T-2101 Coarse: M12 x 1.75mm - T-2102 Medium: M12 x 1.5 - T-2100 Fine: M12 x 1.00mm (Fine XL has the same thread pitch and is a longer version of the fine Traxle)