The Height Gauge is used to establish a baseline and maintain consistency over time when wrapping with your BlueHaus Machine. The Gauge is built with 8.5cm, 9.0cm, 9.5, and 10cm steps for quick reference and adjustability to set and repeat the ideal core height for wrapping. A Height Gauge is included with the purchase of a BlueHaus Machine. This is a replacement part if a gauge is broken or lost.