Maxxis Bicycle Tubes (Flyweight 700x18/25C, Presta 48mm Valve 53g) Flyweight: .45 thin walls. Lightest tube available. Maxxis rim strip (tape) included. Presta valves. Ultralight: .60 thin walls. Lightweight and durable for racing. Available with Presta or Schrader valves. Welter Weight: .90 thin walls. Puncture resistant. Available with Presta or Schrader valves.