Schwalbe Marathon Deluxe HS 420 Evolution Mountain Bicycle Tire - Folding (Black-Reflex - 700 x 35C) Airtightness. Apart from the quality of the ingredients, the purity of the rubber mixture is crucial to the quality of the tube. Reliability. All tubes are inflated and stored for 24 hours in order to test for air pressure retention. Group tube system. Only high elasticity and good quality allows a tube to cover very many tire sizes. Valve. All valves are nickel plated and threaded and valve inserts are replaceable.