In the scene, 8 chair models are prepared and saved, with customized materials: 4 models with leather seats (black leather, gray, brown and white) and 4 models with fabric seats (beige, light gray, dark gray and black).
The models have convenient names.
The materials have convenient names.
The pivot point of the model is aligned to the center of the model, at the lowest point.

The model is assigned the Turbosmooth modifier with Render Iterations mode enabled, for 3 iterations, so that the geometry is meshsmoothed during rendering. In the viewport, the model is displayed without mesh smoothing, for optimal performance.

In obj file the model is saved with applied turbosmooth. Model was done in real world dimensions, system units in scene is mm.

Weight of one chair model, without Turbosmooth, is 9,827 polygons.