A breathable T-shirt for active and everyday wear Shell: 96% Polyester (Recycled), 4% Elastane Our Women’s Siren T-shirt is made with technical knit jersey so it’s stretchy, lightweight, breathable, and durable. It features S.Café® technology, which incorporates recycled coffee grounds in the fiber creation process. As a result, the shirt has UPF 40 sun protection and absorbs odors. The shirt is also a certified bluesign® product.