Carrier Transicold's Trailer Units, Nos. X4 7500 and 7300, offers the highest refrigeration capacities currently offered in a trailer refrigeration platform combined with lower fuel consumption, lower maintenance costs, lighter weight and quieter operation; according to company. The X4 Series also delivers compliance with Tier 4 emissions requirements from the EPA. The units provide 68,000 and 66,000 BTUs of cooling at a setpoint of 35 degrees F, respectively. They also achieve 35 to 50 percent more BTUs of cooling per gallon of fuel, at AHRI rating conditions, than Carrier's current designs.