A very clever device and extremely accurate with many uses around the home , diy or a real time saver if using daily in a professional capacity , you can hold it against a surface until the bubble centres for close at hand work or attach it to a wall or other surface and let the red lazer guide you whilst you work , a magnetic base fixes onto the wall via two large sharp map pins included and the pen then attaches itself to the base with a built in powerful magnet , the pen feels very robust and like a good quality tool , measures just over 5 inches in length and approx one inch wide , approx 3/4 of an inch thick , fits in the pocket although heavy , absolutely fantastic as a levelling guide but doen,t replace the spirit level entirely but i can think of many , many uses and would be lost without it now .