Our Surly TPU tube is made of a tough, airtight material lighter than traditional butyl innertubes. We specifically designed this TPU tube for the Molenda tire, so that we could let loose by making a custom, oversized 6.2" width that maintains its structure, even when operating at low pressures. With the TPU tube installed, you can air-down your Molenda tire to maximize contact patch for excellent flotation and traction over otherworldly terrain.