Nuts are sold separately, if you're looking for a pair buy two!
Tracknuts are heavy-duty nuts with a captive washer.This setup allows you to exert maximum force on the nut without fouling it against the dropout.
Tracknuts are less common than they used to be. Most of our hubs use modern allen key fittings, and the one exception ships with very nice tracknuts as standard.
But if you have an older hub with a threaded axle, tracknuts are a must. Ours are Shimano Dura-Ace, and they're seriously good. We do the matching front nuts, too.
USP is that these take the same 15mm spanner as the rears, despite being threaded for a smaller axle. Simples!