Knight Global's RTA2013 I-Beam Air Balancer Load Trolley for W-Beams transfers loads along the horizontal axis and suspends Knight Air Balancers by the use of the center mounting holes. Knight's RTA Series I-Beam Trolley mounts on overhead W-Beams, I-Beams and Patented Track. Knight Load Trolleys are manufactured from commercial grade pickled and oiled hot rolled steel with a tensile strength of ± 49 ksi and a yield point of ± 30 ksi.