Diesel Glow Plug (ZD17) by Motorcraft®. 91mm from Top of Hex Nut to Seat. If you want to restore the original performance of your vehicle’s ignition system, this product is what you need. Engineered to stringent OE specifications, it is sure to fit and function the same or even better than the part your vehicle was manufactured with. This product is made from premium materials to serve you for years to come.