There are places that that big impact won't go. I've used my Muller-Krups twice in the last week, once on exhaust bolts and once on a transfer case shifter cam plate.
I have one that looks similar. It has come in handy many times and works great. I had another that was a little different style and made of cast metal. It broke the first time I used it.
I had always thought these were a waste of money but since I’ve been working on trucks and having to deal with a lot of stubborn square drain/fill plugs, I’ve found mine to be indispensable. This is a crude, inexpensive wrench extender I got for $11.99 but damn If it doesn’t get the job done...
I use mine all the time. Makes it safer to crank down on a wrench when you’re pulling in an awkward position. It’s a lot easier on the wrenches than doubling them up, too.
I have one without the comfort grip, it makes it easier to fit a cheater bar on. Great for suspension work. If you've ever questioned the quality of your wrenches then this is a good way to test them out.