wheels for easy transport. Road case racks come in different heights based on the 1U standard and different depths. Non-isolated cases simply mount 19-inch mounting posts inside the case. To protect equipment from shock and vibration road rack cases use an inner and outer case. These cases can be isolated by thick layers of foam or may use spring-loaded shock mounting. Touring musicians, theatrical productions and sound and light companies use road case racks. Fiberglass reinforced plastic case racks In 1965, a durable fiber reinforced plastic 19-inch rackmount case was patented by ECS Composites and became widely used in military and commercial applications for electronic deployment and operation. State-of-the-art rackmount cases are now also constructed of thermo stamped composite, carbon fiber, and DuPont's Kevlar for demanding military and commercial uses. Polyethylene molded case racks Portable rack cases using a rotary-molded polyethylene outer shell are a lower-cost alternative to the more durable ATA-approved case. These cases are marketed to musicians and entertainers for equipment not subject to frequent transportation and rough handling. The polyethylene shell is not fiberglass reinforced and is not rigid. The shape of small cases is maintained by the rack rails and the cover seal extrusions alone. Larger cases are further reinforced with additional plywood or sheet metal. The outer shell is frequently embossed in a self-mating pattern to combat the tendency for stacked cases to deform slightly creating a slope that encourages the upper case to slide off. The cases typically use extruded aluminum bands at the ends of the body with tongue-and-groove mating to like bands for the covers. End covers are typically secured with either a simple draw latch or a rotary cam "butterfly" latch, named for the shape of the twist handle. Cooling There is no standard for airflow and cooling of rack-mounted equipment. A variety of airflow patterns can be found, including front intakes and rear exhausts, as well as side intakes and exhausts. Low-wattage devices may not employ active cooling, but use only passive thermal radiation and convection to dissipate heat. For rack-mounted computer servers, devices generally intake air on the front and exhaust on the rear. This prevents circular airflows where hot exhaust air is recirculated through an adjacent device and causes overheating. Although open-frame racks are the least expensive, they also expose air-cooled equipment to dust, lint, and other environmental contamination. An enclosed sealed cabinet with forced air fans permits