Amount of recline the back is set at. This is measured in degrees of angle from vertical. Back pitch is usually set by the manufacturer to meet site conditions. For example, the back pitch for a chair installed on the main floor is often set differently than those in the balcony to help increase comfort by providing proper support. This is most often set between 16 - 24 degrees, but may be more for a planetarium or less for high balcony situations. Back pitch affects the back-to-back spacing.