Loopback terry
A knit fabric with smooth jersey on the outside and uncut yarn loops on the inside. The classic sweatshirt construction.
Loopback terry is the most common construction for sweatshirts and hoodies. A jersey-knit face sits against the body smoothly; the inside is left as uncut yarn loops that trap warmth. It's essentially a domesticated version of the toweling used in bath towels — same loop-pile structure, finer yarns.
When the loops get sheared (cut and brushed), it becomes "fleece" or "french terry." Loopback specifically is the unsheared version, lighter and more breathable than fleece, with a flatter, more refined surface. It's the construction Champion built its reputation on; today brands like Reigning Champ, Lady White, and Fanmail keep the heritage going.
Weight typically runs 380–500 GSM. Lighter loopback (around 380) wears like a heavy long-sleeve tee; heavyweight 480–500+ is sweatshirt-proper, structural enough to hold its shape over years of wear.
GSM
Grams per square meter — the standard unit for fabric weight. Higher GSM = heavier, denser, often more durable.
French terry
Loopback terry with the inside loops sheared and brushed for warmth and softness. Heavier and warmer than loopback; less defined surface.
Pilling
Small balls of tangled fibers that form on fabric surfaces from friction. Tells you about fiber quality, knit construction, and how the garment was made.