The SP-100 Air-Powered Adjustable Speaker Sub Pole features an expanding cylinder system that will firmly fit multiple speaker sockets from 3/8" to 1/2" diameter. Air-Powered Series sub poles from Ultimate Support are incredibly strong, sturdy, lightweight, and raise and lower speaker poles on their own. The stands in the Air-Powered Series feature an internal shock that lifts speakers weighing 25 lb. or less with no effort, and only requires one hand to raise speakers weighing more than 25 lb.