Az "air bellows" magát a légrugót jelenti.

"Usually, each axle assembly has two air springs behind the axle."
http://www.contitech-usa.com/products/airspringsOE.html

...people are becoming more comfortable with the idea of replacing a metal-wound coil spring with that of a rubber bellows type cylinder (air spring). www.rodandcustommagazine.com/howto/4928/

Air spring: load-carrying component of an air suspension system used on machines, automobiles and buses.
A system used on buses consists of an air compressor, an air-supply tank, leveling valves, check valves, bellows, and connecting piping. Basically, an air-spring bellows is a column of air confined within a rubber and fabric container that looks like an automobile tire or two… http://www.britannica.com/eb/article-9005213

A bellows formát a "convolutions"= elválasztó gyűrűk adják.

A "two bellows" a rendszerről beszél, ami lehet 2, 2-2, vagy több:
"Two bellows on front axle, four on rear axle, all interchangeable." www.man-mn.de/en/Coaches/News_&_Media/ Press_releases/show_press.jsp?key=53072&lang=en