Smartwares Trailer Light Tester for Semi Trailers (TLT Tool) Saves you on maintenance, loadup costs and time! And no more Tickets! Check Semi-Trailer lights without Hooking up cab in under 1 minute by yourself! Plugs directly into Semi-Trailer lighting Power conduit with built in trailer adapter. Lightweight portable, waterproof design easy use and store. 5 Yr Warranty! Rechargable 12V 3-5yr battery tests a whole fleet in a day.