The Electronic Specialties Mini Back Probes/Wire Piercers, No. 618, are designed to save time and increase productivity by making some of the more difficult testing connections easier. These can be used to back-probe weather pack-style connectors, found on many automotive sensors. Other applications include piercing and tapping readings on smaller gauge wires using the included probe adapters. The probes work with most test lead kits with a standard 4mm banana plug test lead connection. The set includes four probes in red, black, green and yellow. Test probes are 21mm in length.