In sports clothing, small measurement variations—known as tolerances—are normal and expected due to the nature of textile production. Fabrics stretch, shrink, and behave differently during cutting, sewing, and finishing, which means that even with precise patterns, every garment reacts slightly uniquely. Performance materials like polyester blends, moisture‑wicking fabrics, and elastane also have mechanical stretch that can change the size by a few millimetres during handling. On top of this, garments are assembled by hand or semi‑automated machinery, and each seam, fold, or stitch can introduce minor differences. Because of these combined factors, manufacturers allow a tolerance range (typically ±1–2 cm) to ensure consistent quality while acknowledging that perfect mathematical precision isn’t achievable in textile production. It is perfectly feasible that you could try on (for example) a large tee (but made to the upper end of the tolerance) and an extra large (made to the lower end of the tolerance) and there exist very little between the two sizes. This is though dependant on the brand you are wearing.