Professional quality Speed Bow Compass adjusts two ways: press the buttons on the legs for extremely fast adjustments or use the center wheel for fine adjustment. Each Speed bow compass features: Protruding buttons on each leg for increasing or decreasing the width between the compass legs Detachable legs for using extension leg, adaptor, or ruling pens Various wheels for easy adjustments and detaching Universal adaptor & additional premium lead The case has empty spaces for additional accessories available separately. This set includes an extension bar.