The only reason this unit gets four stars is because it is more expensive than competing units. In terms of functionality, it's proven spot on in our tests and is a real time saver in the field, as well as for checking the length of wire left in the box before a long pull, not to mention a tremendous help in troubleshooting. . We were able to avoid cutting holes in the finished drywall because we were able to narrow down the location of breaks and shorts when troubleshooting Cat5/6 and RG-6 wiring.