The product category set in the recommender's product information template is not just a label. It controls four things at once:
Which questions the shopper is asked
How much room the garment is assumed to have
Which measurements count toward the size recommendation
Which illustrations appear
The most common mistake
Setting a jacket up as a shirt. A men's jacket assumes 17 cm of chest room and a shirt assumes 10 cm — often a full size of difference in the result.
When nothing matches your garment
Choose the nearest category by how the garment fits rather than by its name, then correct the difference with the ease setting.
For example, a tailored gilet behaves more like a blazer than a sleeveless shirt — set it up as a blazer and adjust ease if needed.