Materials and care. 95% cotton/5% elastane. Wash at 30 Please note, all underwear items are non returnable. Stylist Notes. Arriving in a classic fit, this Calvin Klein 95% cotton/5% elastane for added stretch underwear is a staple set for your wardrobe. With a breathable cotton with a soft feel, they combine both practicality with style. Please note, all underwear items are non returnable.