The Phil Wood ISO high-flange track hubs have wider 3.5-inch flanges. Phil's current high-flange track hubs have 3-inch flanges. The news is that just like a disc rotor, you can bolt on your rear fixed cog. No lock ring wrenches, my greasy cats. No possibility of stripping threads, cross threading a cog, or gouging a lock ring. The rear hub includes the necessary bolts, which take an allen (hex) wrench. And you can buy the bolt-on cogs in the sizes you prefer. Oh, how nice will it be to change cogs with a wrench that fits on my key chain? Front hubs are 100mm standard spaced.Rear hubs are available in 32H and 36H with 120mm spacing. "The hub is offered in a single-fixed, double-fixed, fixed-freewheel, and
fixed-freewheel (White Industries freewheel-specific) configuration.
Cogs are available only in 1/8″ and in 16-20 teeth." According to Phil, use their bolts, so the bolt and thread fit is golden. These are solid and weighty babies. (Two hubs and a Happy Birthday to all Gemini twins!)
(Photo by Wheelgirl and silver ISO High-Flange Track Hub pix lifted from Phil website.)