Metrel Probe & Test Leads Safety test lead 623526 - Metrel 20991115, Metrel A 1153 safety test lead, featuring 4 mm jack connectors on both ends, in a 20.00 m length and black colour. This test lead is designed for safety and reliability in electrical testing applications. It is typically used by technicians for connecting and testing electrical circuits and devices. Metrel 20991115 Safety Test Lead 20m Black 4mm Jack for Earthing Use