GSM (grams per square meter) is the standard measurement for fabric weight, indicating how much a square meter of material weighs. In streetwear, GSM has become shorthand for quality assessment: higher GSM generally means thicker, more durable, more premium-feeling fabric. Lightweight t-shirts typically range 120-180 GSM—fine for summer basics but prone to transparency and wear. Mid-weight garments run 180-250 GSM, offering balance between comfort and durability. Premium streetwear gravitates toward heavyweight territory: 250-300+ GSM for t-shirts, 400-500+ GSM for hoodies and sweatshirts. These heavier fabrics hold structure better, drape cleaner, resist pilling, and feel substantial. However, GSM alone doesn't determine quality—yarn quality, knit construction, and finishing matter equally. A well-constructed 250 GSM tee may outperform a poorly made 300 GSM one. Understanding GSM helps consumers evaluate what they're paying for and compare products across brands. Many streetwear enthusiasts specifically seek heavyweight options, viewing substantial fabric weight as a marker of quality investment.