If it is the same as my 300E, there is a button on the back of the seat panel. You raise the headrest as far as it will go with the electric switch and then depress this button on the back panel of the seat and pull the headrest out. The button looks like a round-ish depression in the rear seat panel, near the center of the panel.

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Chris
2007 E550 4Matic - 61,000 Km - Iridium Silver, black leather, Sport package, Premium 2 package
2007 GL450 4Matic - 62,000 Km - Obsidian Black Metallic, black leather, all options
1998 E430 - sold
1989 300E - 333,000 Km - sold
1977 280E - sold
1971 250 - retired

"And a frign hat. They gave me a hat at the annual benefits meeting. I said. how does this benefit me. I dont have anything from the company.. So they gave me a hat." - TheDon