The X4™ Series. Renowned for its high capacity, efficiency and dependable performance. Ultra-high capacity. Delivers our highest capacity along with fast pulldown, precise temperature control and peace of mind for the most demanding applications. High efficiency. EcoFORWARD™ technologies deliver significant fuel savings as well as higher performance, lower operating costs and compliance with EPA Tier 4 emissions regulations. Proven reliability and lower cost of ownership. Combining innovative engineering with a straightforward, practical design means reduced engine run hours and lower maintenance costs. APX™ control system. Remarkable control intelligence for precise temperature management and amazingly simple operation. More sustainable refrigerant. Sustainability enhanced through use of R-452A, a refrigerant with lower global warming potential.