Originally Posted by silver_ghost

The S3X does have a "neutral" between low and middle but don't get any ideas about being able to switch between fixed and freewheel on the go. The first run of S3X shifters had the shift detant in the wrong place, allowing the hub to pop out of first gear into neutral. I had one of these shifters and when the hub popped out of and back into gear, the internals were damaged, leading to a gross grinding feel while pedaling.

To SA's credit, when I emailed the company they were forthcoming about their mistake and sent me a new shifter and entire new hub internals within days. Since installing the new shifter and hub guts everything has worked just fine.

Just to clarify about the S3X driver, it uses a Shimano cassette spline pattern without the big and little spline. Shimano stamped single speed cogs don't fit, but machined Surly or (I assume) Sturmey Archer ones do. The driver is threaded to accept a BMX freewheel.