3AL Aluminum Cylinders for the AirHawk II SCBA are less expensive than MSA's Hoop-Wound cylinder. This 30-minute low-pressure cylinder comes filled/pressurized with air and features all-aluminum construction. Because of its weight (approximately 18 pounds), it is designed primarily for customers who don't use an SCBA frequently. The 3 AL Cylinder also offers an indefinite service life. Unlike composite cylinders, it does not have to be retired after 15 years of use, provided the cylinder meets the requirements of the hydro test, which must be done every five years