Lambda Plug M18x1.5 - 5/16" Hex A lambda plug is a bolt with a wide sealing surface against the bolt head to easily block an outlet such as a lambda sensor hole or other holes with an M18x1.5 thread. No washer seal is required for the plug to remain tight as it flares out against the head. However, a washer can be advantageous to prevent it from loosening due to vibrations. Specifications: Thread: M18x1.5 Weight: 34g Length: 16mm~ (UHL: 11.5mm) Sealing surface between thread and bolt head: ~2.5mm Material: Stainless steel (Threads are cold-worked, making them slightly magnetic) Hex size: 5/16" Hex