This is a custom machined spark plug tool designed and made by another Porsche enthusiast (aka Syderman2). This tool hits all the important points:  

1. Works on all 718 4.0 engines (GTS, GT4, GT4RS, Spyder, Spyder RS).

2. Extension is permanently attached to minimize challenging removal of lost socket.

3. Magnetic holder for spark plug inside the socket

4. Nearly half the price and easier to obtain than the Porsche official tool. 

5. Includes appropriate extension and u-joint swivel making the spark plug change easier.

6. It's made by a Porsche enthusiast FOR Porsche enthusiasts!

In my YouTube video detailing the keys to success of changing the spark plugs on my GT4, I mentioned that the Porsche socket (~$180!) was the only socket capable of getting the job done.

That is no longer the situation.

Thanks to this custom machined  socket with extremely thin walls, magnetic hold, flex extension and detachable u-joint swivel - it exceeds the capabilities of the original Porsche socket. Made from chrome-vanadium steel. You will not find any other socket that meets all these requirements, and there are no other thin walled sockets like this. GTS 4.0, GT4, and Spyder requires a socket no larger than 17.7mm in diameter.  I still offer the Porsche socket for rental if you prefer, but this socket finally makes the purchase worth it at the price and will make the job so much easier.