GSM — grams per square metre — is the standard unit for fabric weight in the textile industry. It is a measurement of mass density: how much fibre is packed into a defined area of fabric. It is not a measure of quality on its own. But in combination with fibre type and construction, it tells you most of what you need to know about how a fabric will behave.
The Signature Fit jersey is 180 GSM. That number is the result of a specific set of decisions, and it is worth explaining what each of them means in practice.
Why not lighter
Lightweight jersey — typically 120 to 150 GSM — is common in fashion T-shirts because it is cheaper to produce and creates a visual silhouette that photographs well against a white background. It is also translucent, clingy in humidity, and degrades faster under repeated washing because there is simply less material to sustain.
A 160 GSM fabric is a reasonable middle ground — adequate drape, some opacity — but it sits in a zone where the trade-offs are not fully resolved in either direction. It is not as economical to produce as 150, and it does not achieve the structural integrity of 180.
At 180 GSM, the fabric reaches a threshold. It has enough mass to drape under gravity with a natural fall rather than clinging to the body. It is fully opaque in standard lighting conditions. It has enough fibre density to absorb and hold moisture without feeling wet. And it has enough structural mass that after fifty washes, the fabric retains its shape rather than thinning to the point of translucency.
Weight is not luxury. But the absence of adequate weight is almost always a compromise.
Why not heavier
Beyond 200 GSM, jersey fabric begins to lose some of its defining properties. It becomes less responsive — slower to recover from deformation, heavier on the body, less suited to the kind of everyday garment that is worn through movement and temperature change. The sweet spot for a T-shirt — a garment intended for direct skin contact, worn through varied conditions, washed frequently — is narrower than it might seem.
At 180 GSM, the Pima jersey is heavy enough to feel substantial in the hand, to hold its structure across the chest, and to maintain dimension through washing cycles. It is light enough to remain comfortable in warm conditions and to not impose itself on the body.
What Pima adds to the equation
GSM in Pima cotton is not directly comparable to GSM in standard cotton, because the fibres themselves are different. A 180 GSM fabric knitted from 39mm Pima staple has different properties than a 180 GSM fabric knitted from 28mm upland cotton at the same weight.
The longer fibre produces a yarn with fewer protruding fibre ends at the surface. The fabric feels smoother at the same weight. The yarn can be spun finer at the same strength, which means the 180 GSM can be achieved with a finer, higher-count yarn — producing a fabric that is simultaneously heavier and smoother than its upland equivalent. This combination — mass without roughness — is specific to long-staple construction.
180 GSM in Pima cotton is a different thing than 180 GSM in standard cotton. The number is the same. The material is not.