Rugged, fully enclosed frame; no exposed fittings or hoses. Runs on air. Secondary back-up filtration system for reliability. Light weight for greater mobility and positioning. Automatically controlled, "chatter free" load lowering for maximum safety in descent. All Pow'r-Riser models come with ASME/ANSI B30.1 Specifications. Warning: Any two extensions may be stacked for loads up to 60 tons per jack. For loads from 60 tons to 150 tons only 1 extension and 1 spacer can be used.