I wanted to try it on a bunch of different saws, so, after testing it on the mix of working and non-working saws that I could access at home, I stopped by a couple of local saw dealers to try it on their floor models, and get their input. I can't say that it will work on every saw (I did not have any full wrap handles to try it on), but it fit pretty much every saw I tried, including: consumer, mid range, and pro saws from a variety of manufacturers, and of different vintages, as long as they used the 13mm or 19mm bar nuts.
On some saws, the bar nuts are recessed deeper into the clutch covers, leaving little to no hand clearance, and requiring the handle to be tilted at a steeper angle. The wide 'stirrup' holding the pivoting socket might interfere with deep recessed covers on some saws. Compatibility can only be confirmed by trying the tool with a specific saw.
OTT provides special bar nuts described to provide 'more surface contact' with the magnetic socket. These bar nuts are noticeably taller than the OEM STIHL and Husky nuts, so they should help with deep recesses on clutch covers (unless they are 'captured' nuts).
One thing that this scrench will
not work on is spark plugs; the compact socket does not have a hole for the electrode to fit through, even if it did reach. So, if you pull your plugs frequently, you would need an additional tool, like a standard scrench, or an automotive type spark plug socket in your tool kit.
Philbert