STL-4 Solar Test Leads For MC4 Solar Connectors 1000V/19A CE Warning Labels MC4 Solar Test Leads are designed for current and voltage measuring on PV-modules and systems. They connect directly to PV modules or strings with multi-contact MC4 Test Plugs and sockets fitted with gold plated contacts and allow safe connection of a multi-meter or voltage detector whilst proving the system. They significantly speed up testing time, and are an essential tool when carrying out live/dead testing.