VITTORIA Air-Liner Tubeless Insert - MTB, Medium, 2.25-2.50"The Air Liner is a high quality polymer insert, which replaces a portion of the air volume in the tire. This trait, combined with the shape, provides a tunable system that enhances your ride performances. The Air Liner destroys the traditional compromise of stability vs. grip, and allows your tires to remain stable, grippy, and controlled, even at low pressures. The Air Liner is designed using a round cross section, with channels on the top and