Helical gears transmit rotary motion and power between parallel shafts. They have disc-shaped bodies and slanted teeth that curve to the right or left of their axis. They come in pairs with the same pitch, angle pressure, and helix angle but have opposite-facing teeth. Their inclined teeth mesh gradually and stay in contact longer than straight-cut gears, which creates less noise and vibration and enables them to handle larger loads and higher speeds. Helical gears are interchangeable with spur gears of the same module and number of teeth. Typical uses include automotive transmissions, machine tools, and industrial gearboxes.