When sourcing stretch chiffon, the primary focus should be on the blend ratio of polyester and spandex (elastane). A standard high-quality blend typically consists of 95% polyester and 5% spandex, providing the characteristic 'give' while maintaining a lightweight feel. You must verify the fabric weight (GSM - Grams per Square Meter); for stretch chiffon, this usually ranges between 70g to 130g. Additionally, check for colorfastness to rubbing and washing (Grade 4 or higher) to ensure the fabric does not bleed or fade during garment production or consumer use.