The Tioga Thorn-Resistant Schrader Valve Tube 18x1.90-2.125" 40mm is a tough, reliable inner tube designed to reduce flats from thorns and debris while providing a secure fit for a range of 18-inch tires. Built from durable butyl rubber and fitted with a 40mm Schrader valve, it offers easy inflation and dependable air retention for everyday riding and trail use.