Piqué, jersey, and the intended hand feel.
Fabric establishes how a polo hangs, how the collar relates to the body, and how the finished garment feels against the skin. Cotton piqué, smooth jersey, and suitable blended constructions offer different starting points. Specify the surface texture, weight, stretch, and opacity you want instead of using a single fabric name as the entire brief.
For a performance-oriented range, define the intended activity and any performance claim separately. A sporty appearance does not prove moisture management or durability. For a fashion collection, a substantial hand feel may matter more than an athletic fit. Material development should follow the product position, with swatches and garment samples reviewed together before fabric approval.