accumulator spool

actuator spool

actuator spool deadband width

adaptor spool

affected control valve compensator spool

apron control valve spool

arm spool pin

armature spool

articulated spool piece

attachment spool assembly

attachment valve spool

automatic spool

auxiliary valve spool

blind flanged spool piece

blowout preventer and spool

bobbin spool

body hoist spool

boom control spool

boom control valve spool

boom cylinder control valve spool