Strauss Bicycle Speedometer, (Black/Red) Pack of 12 Multi functions with auto sleep and wake-up its records speed in mph/kmph, riding time, distance, scan, maintenance alert This bicycle speedometer is waterproof and works great on rainy days as usual when riding Portable size, light weight, wide application this bike odometer is only for 1.8 x 1.8 inches (l x w) and 0.18 lb, which is easy to carry and save your space Easy to install and use it is easy to follow instructions, great basic functions of the speedometer and very specific tire size that enable accurate calculations Material: Plastic