About A Chair AAC 252 office chair by Hee Welling

HAY describes the AAC 252 as having "a five-legged castor base" and "a shell with a slightly higher backrest," with "a deep, generous seat." As with the AAC 212, 222, 226, and 220, the armrests are low: they support the forearm while allowing the chair to slide under a desk.

The shell: recycled polypropylene, what HAY calls "2.0"

The seat and backrest form a single injection-molded shell made from post-consumer plastic waste: this is what the "2.0" in the color names refers to. The material is solution-dyed: a scratch will not reveal a different color underneath, and maintenance is limited to soapy water. On lighter shades, slight variations in hue are inherent to recycled materials.

The base: five-legged, castors, and gas lift

The base is a cast aluminum five-legged star: HAY refers to it as a cast aluminium five-legged castor base: mounted on castors. Five legs rather than four: this is the stability standard for rolling chairs, as a four-legged chair tips over too easily when leaning forward.

A gas lift adjusts the seat height. It is a pneumatic cylinder: a pressurized nitrogen cartridge, operated by the lever under the seat, which lifts the chair effortlessly and locks it at the desired height. It requires no maintenance and can be replaced as a spare part if it eventually loses pressure.

Note on height dimensions. HAY publishes a single overall height for these chairs. Since the seat is adjustable via gas lift, this value corresponds to a specific position, not a fixed height.