Abstract: A sprag clutch having inner and outer concentric races 1, 2 with sprags 3 pivotally located between the races 1, 2. A circumferential garter spring 6 locates over the sprags 3 to bias them to a wedging position. Relative rotation of the races 1, 2 in one direction causes a centrifugal force CF to act on each sprag 3 to pivot away from contact with the outer race 2. The center of gravity G of each sprag 3 is located radially inwards of its center of rotation C such that when the sprag 3 pivots the centrifugal couple CF increases to overcome the increased tension couple SF of the garter spring to allow a snap action lift off of each sprag 3. The perpendicular distance of the center of gravity from the pivot center of each sprag increases during pivoting to cause an increase in the centrifugal couple. At the same time the perpendicular distance of the pivot point of action of the resilient mean from the pivot center decreases during pivoting.