The Polar Speed Sensor Set W, I, N, D, is black, It is made of leather, It measures cycling speed and distance via a magnet rotating on wheel, It features easy attach and aerodynamic design, It is compatible with the Polar cycling computer, Measures your current, average and maximum speeds, Interferencefree data lets you evaluate and analyze your individual performance more accurately, Easy to install to stem or handlebar, Easily attach and detach your cycling computer with the twist locking mechanism, Dimensions: 11, 5L x 0, 75W x 4H, SKU: SPTMN4627