Tree Flyer 2: Quality Improvements : r/Allbirds。Allbirds Tree Flyer 2 running shoes in a sleek black and grey colorway with a distinctive geometric cream midsole. These performance sneakers are crafted with a breathable eucalyptus tree fiber upper and feature a bio-based SwiftFoam midsole for high-rebound cushioning. Designed for stability and speed, they include a secure lace-up closure, heel pull tabs for easy entry, and a durable FSC-certified natural rubber outsole for excellent traction. The heel displays the 5.88 kg CO2e carbon footprint mark, highlighting the brand\'s commitment to sustainability. Note some light discoloration on the midsoles from previous use.