The Sperry-Sun Adjustable Gauge Stabilizer (AGS™) tool
is a hydraulically actuated integral blade stabilizer with
three straight or spiral blades. Each blade carries four or
five pistons which are extended by the differential pressure
between the inside of the AGS tool and the annulus, and
retracted by a spring. In order to obtain a fast and positive
action, a pressure differential of 450 psi (31 bar) is recommended.
The pressure drop through the AGS tool itself
is negligible when the pistons are flush, and 150 to 250
psi (11 to 17 bar) greater when the pistons are extended