About A Chair AAC 153 office chair by Hee Welling

HAY describes the AAC 153 as combining “optimal functionality with a modern aesthetic,” while retaining “the high backrest and generous seat that characterize the series.” It is the only model in the range for which the brand publishes the exact gas lift travel.

The upholstered shell, and what the textiles are

The shell is the same as on the non-upholstered models, a molded recycled polypropylene—that is what HAY's product sheet says—but here it is covered over its entire surface. Foam is applied to the shell and then finished with the chosen upholstery: the contact is softer, and noise is better dampened in high-traffic rooms. Conversely, upholstery must be cleaned by dabbing rather than with a jet.

The upholstery options offered here: Sense, HAY’s aniline leather, dyed through: it allows the grain to show and patinates with use. The so-called quilted variants—HAY uses the term quilted—feature topstitching that compartments the padding: the stuffing does not shift over time, and the texture breaks up the uniform surface.

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

The base is a five-star cast aluminum star—HAY writes cast aluminium five-legged castor base—mounted on castors. Five legs, not four: this is the stability standard for rolling chairs, as a four-legged chair tips too easily when leaning forward.

A gas lift adjusts the seat height. It is a pneumatic cylinder: a pressurized nitrogen cartridge, activated by the lever under the seat, which raises 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.

HAY publishes the gas lift travel for this model: 14 cm of seat range. It is the only reference in the series for which this value is provided.

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