ID these things please.

You made me curious, so I searched and found this...:oops:
http://www.wkjeeps.com/wk_engine_heater.htm

Apparently it mearly contacts the metal of the block and is not immersed in coolant. Hmmmm.
"The 5.7L/6.1L engines have the block heater located on the left side of the engine below the exhaust manifold in the rear of the engine. It is not immersed in engine coolant but makes direct contact with the block."