Calibrated shrouds make accurate charging simple and the charge is measured by weight for greatest accuracy. Using the calibrations in conjunction with the pressure gauge, you can easily compensate for volume fluctuations that occur as the ambient temperature changes just by "re-dialing" the shroud. Heated cylinders help speed the transfer of refrigerant by overcoming the equalization of pressure between the system and the charging cylinder. This reduces the time required for a complete charge. Charges by volume; calibrations on the shroud make it easy to charge the exact amount required. Comes in durable polyethylene case for protection during storage and transit. Cylinder snaps in and out of the case and can be stored either vertically or horizontally. For safety, all cylinders come with pressure relief valves; they automatically reset when a safe working pressure is restored. 5lb./2200 gram, 110V, ACME fittings