Black Allbirds ballet flats. Size 9. See photos for nice condition Breathable Knit Made From Natural Materials for All-Day Wear. Lightweight, breathable, and effortlessly sleek, the Tree Breezer is your go-to flat. Best For: Day-to-night, warmer weather, everyday wear Thermoregulating Material: Lightweight, breathable eucalyptus fiber provides next-level comfort Versatile Design: Wear-with-everything classic style, great for the office Sustainable Materials: FSC-certified TENCEL™ Lyocell (eucalyptus tree fiber) upper SweetFoam® midsole made with sugarcane-based green EVA Castor bean oil-based insole foam It has a carbon footprint of 2.7 kg CO2e.