Air line fittings servo retract control valves Retract control valve for air up & down in 5 and 3 nipple versions with 1/16″ barbs, for use with a servo to control the valve. Air line fittings servo retract control valve air up & down 3 nipple 1/16″ barbs Type Price 5 nipple, per valve £ P.O.A 3 nipple, per valve £ P.O.A