Glossary
GSM
Also called: grams per square metre, fabric weight
GSM (grams per square metre) is the standard measure of fabric weight. Lightweight tees sit around 120 to 150 GSM, midweight around 180, and heavyweight garments 200 and above.
GSM is the closest thing to an objective quality signal on apparel, which is why it is worth quoting in listings. A buyer comparing two identical-looking shirts has almost nothing else to go on.
Higher is not automatically better. A heavyweight tee feels substantial and sells well as a premium item, but it is the wrong choice for a summer product, and it costs more to ship.