This adapter is designed specifically for adding electric gauge senders (or a sender and a mechanical pressure hose) to an M16 port. Male 16x1.5mm threads at one end screw into your port, and female 16x1.5mm threads at the other end can accept whatever was screwed into the port before. Dual 1/8 NPT female ports accept any electrical sender with 1/8 NPT male threads.
The steel adapter has a PTFE coating to aid in sealing. Includes an aluminum crush washer for the M16 port, and plugs for the NPT ports. Sold individually, gauge senders not included. Color may vary from photo.