What is a spacer bra? Spacer Bras are a lightweight alternative to your usual padded bras. The difference lies within the fabric – it’s all about the Spacer Fabric. It’s created very differently to regular foam as the purpose is for it to be light and breathable. Spacer Fabric is a 3D knitted fabric (constructed of 2 layers of thin fabric, joined together with a spacer yarn), designed to create air flow and light padding. (From Panache Lingerie)