GSM — grams per square metre — is the weight of a fabric. It tells you how dense the weave is, how much raw material went into it, and ultimately, how it's going to hold up over years of wear.
The Numbers
A standard fast-fashion tee runs 140–160 GSM. A mid-tier hoodie from most brands: 280–320 GSM. At 400 GSM, you're in territory that most brands won't touch because the fabric cost alone prices out their margins.
We don't care about that. We care about what it does to the garment.
What 400 GSM Actually Feels Like
It hangs differently. A 400 GSM garment has structural integrity — it holds its shape through a wash cycle, it doesn't pill after three wears, and the drape is controlled rather than floppy.