From Fit2Sew:
Foam padding is a ideal for use as cut-and-sew cups in patterns such as the Sapphire partial band bra and the Ruby and Amethyst full-band bras. It is lightweight and non-itchy and is finished on both sides with a chlorine-resistant soft polyester knit fabric, making it ideal for swimwear too. This foam padding is also good for padded straps to give extra comfort, as featured in our Ingrid findings kits.
100% polyester.