Twist-Lock Pigtail has been around for 40+ years. It's ideal for shallow and exposed glow plugs. It produces a secure connection and a great look on all crafts especially scale Airplanes. Another bonus is we have terminated the ground wire on the shell, so no need to install a ground connection to your motor or backplate. Best choice for Airplanes, and smaller engine Cars, Trucks, and Boats. Will require long nose pliers to install on deeply sunk glow plugs.