Ecobra Speedmaster Giant Bow Compass and Extension Bar This compass features \"Speedmaster Quick Release\", Ecobra\'s unique design and construction which combines rapid setting and fine adjustment with automatic locking on the spindle at the chosen setting. It also features an all metal construction with spring loaded levers for rapid setting, two knee joints and 4mm spigots. Supplied with compass, pencil and lengthening bar. Length 170mm (6. 8\") and a working range of 560mm (22\") diameter. Not suitable for use with technical pens.