Depending on tool size, each AGS ™ stabilizer blade carries four or five pistons. If there are five pistons, there are five activating ramps. Each ramp activates three pistons, one on each blade. All the ramps move together. When differential pressure pushes the ramps under the pistons, the pistons are displaced outwards. Piston extension and position indexing is controlled by a barrel cam. The pistons are held in position against stops by the differential pressure. When the mandrel carrying the ramps is moved downwards by pump pressure acting on it, the ramps displace all the pistons simultaneously. The pistons move outwards from their rest position and are held against a stop in the barrel cam by the differential pressure. When the pressure is removed by shutting down the pumps, an internal spring returns the mandrel to its start position thus retracting the pistons and indexing the barrel cam to the next position. Bringing the flow rate back again will cycle the AGS ™ from rest to the next operating position, where the pistons will again be held against the stop in the barrel cam by the differential pressure. When the pressure is reduced as before, the pistons are again retracted below flush. The pistons are held in their extended positions until the pumps are cut. Weight on bit plays no part in setting the tool or holding the setting.