I have been using that hub on my folder for about a decade. I could not fit a front derailleur to the folder due to frame design, wanted wider gearing and that was the best option. It is a three speed hub, middle gear is direct drive, third gear is overdrive, with a 8 or 9 speed freehub. Dropout spacing 135mm, solid axle only.

In my case I bought the Sram Dual Drive hub (now discontinued) to use with a drop bar bike that I had built up years earlier, was using bar end shifter on the derailleur. And got lucky and found that a Sturmey Archer three speed bar end shifter had the correct indexing for the hub, even though it was a different manufacturer. On flat ground I am using the overdrive, this gives me much lower gearing for hills. With an eight speed cassette (11-32), my total gear range is 540 percent, with a 20.8 gear inch low gear.