Heavy duty chairs
Standard office chairs are typically rated to around 110kg. Heavy duty chairs are built with stronger frames, bases and gas lifts for use above that.
Check the rating, and check it honestly
A chair used above its rating does not fail gracefully. The gas lift goes first, then the base. Buying to the rating is a safety matter rather than a comfort preference, and it is worth handling as a normal part of specification rather than something awkward.
What else changes
Heavy duty models usually have a wider seat and a stronger five-star base, often steel rather than nylon. If the chair is for full-day use, the same task chair adjustment rules still apply on top of the rating.
Ranges we stock
Heavy duty models sit within the Chiro and Ergo families, with reinforced bases and higher-rated gas lifts. The usual task chair adjustment rules still apply on top of the rating, and replacement gas lifts and castors are stocked separately.