On Thu, 20 Jan 2005, SkiFit wrote:

The original NNN system rembled NNN2 where the binding meets the boot,
but did not have the grove binding/boot interface. With the grooves,
there is now greater connection between binding and ski, which allows
for greater control and energy transfer. NNN and NN2 systems NNN-BC
(backcountry) resembles the old system, but is both wider and
presumbably heavier duty for true back country skiing. However, I
think most backcountry/telemark skiers continue to use three-pin. I
ski on skinny skis, so I'm not sure about advantages there. Each of
these systems is distinct and cannot be used with the other, and I
doubt you coud buy NNN now, it has gone the way of the Super Eight
camera.

Part of this is mistaken. NNN and NNN2 both have the same grooves
in the front of the boot. NNN2 extended the grooves the full length
but they are unchanged in the front. The differences were so minor
that all that was necessary to put an NNN2 boot into an NNN binding
was a modified flexor. These were available for sale for a while
during the changeover period. I still have NNN bindings with the
modified flexors on some of my rollerskis because there's just no
compelling reason to replace them.

-Mitch