Brand New - No Box. Women’s 11 (41 EU) Or Mens 9.5 (42.5 EU). Retail $150. Non Smoking Seller. Tried on but didn’t fit. The new Tree Flyer performance running shoe from Allbirds is said to have a carbon footprint of 9.92 kg CO2e, all of which is offset to zero. Created at what Allbirds calls the intersection of innovative technology, renewable natural materials, and instantaneous material circularity, the Tree Flyer is said to have more bounce, more propulsion, and a 70% rebound rate that helps give runners more energy with every step thanks to SwiftFoam technology.