These lightweight, powerful instruments can be used to search for large or very small treasures. The antenna length can be adjusted according to whether you are looking for close by or distant targets. You shorten the antenna if you want to find only sources of attraction that lie close by and extend the antenna when searching for more distant targets. You can use the instruments for both short and long range work when the antenna is fully extended.  It can be used to search for specific metals or minerals by installing a sample of that metal or mineral in the sample compartment. Each is individually built...not mass produced. All the Anderson directional locating instruments listed are "self potential", which means they do not rely upon outside sources (batteries) for power. It can be used to search for specific metals or minerals by installing a sample of that metal or mineral in the sample compartment.