The document details the history and specifications of the "Big Rig", a mobile refrigeration unit used by the NHL to host outdoor hockey games. It lists the various outdoor games hosted from 2009 to 2016, including the Winter Classic and Stadium Series events. It also provides the technical specifications of the Big Rig, including its refrigerant type, compressor models, heat exchanger, pumps, trailer details, and electrical requirements. The Big Rig is a 310-ton mobile refrigeration system powered by ammonia compressors that is used to maintain ice conditions for outdoor NHL games.