When sourcing Cotton Lycra (also known as Cotton Spandex), the ratio of cotton to Lycra is the most critical factor. A standard high-quality blend is typically 95% cotton and 5% Lycra, providing the ideal balance of breathability and elasticity. You must verify the fabric weight (GSM - Grams per Square Meter); for T-shirts, 160-200 GSM is common, while leggings require 220-300 GSM to ensure non-see-through quality. Additionally, check for combed cotton rather than carded cotton to ensure a smoother surface and reduced pilling.