T1N Glow Plug and Module Kit
This is the newer style glow plug module (aka "relay") that has self resetting circuit breakers. Made by Hueco, an OEM supplier to Mercedes.
The glow plugs (5 of them) are OEM Bosch and are recommended over the "auto parts store" glow plugs that I personally have seen only last ONE YEAR!
I am now recommending that the Glow Plugs and Glow Plug Module be changed out as a part of the 100K mile or 10 year (which ever comes first) maintenance schedule.