This item is manufactured with premium material for durable and long-lasting use. The GT2 series of belts are specifically designed for linear motion. They use a rounded tooth profile that ensures the belt tooth fits smoothly and accurately into the pulley groove, so when you reverse the pulley direction, there is no room for the belt to move in the groove. Features - Color: Shown in the pictures. - Material: Aluminum. - Size: Approx. 5 * 3 * 0.8 cm / 2 * 1.2 * 0.31 inch (L * W * H). - for durable and long-lasting use. - GT2 timing belts and compatible pulleys (GT2 pulley) are good choices for RepRaps and RepStraps. - Specifically designed for linear motion. - For best performance, you want at least 6 teeth in contact with the pulley at any given time. That minimizes the chance of the belt slipping and helps to reduce backlash further. In practice, that means you want at least a 12-tooth pulley, and I usually try to get at least 32 teeth.