For what it's worth, track nuts will cost about the same, don't require a socket to install but instead work with a standard 15mm wrench, will let you crank your nuts as hard as you want(!), don't come with a flanged washer to chew the hell out of your forkends, don't fall into multiple pieces when off the bike, and can be had at most bike shops that carry fixed or SS gear.

I'm not saying the Primo's won't work, but I think they're probably appropriate for BMX and you'd have fewer hassles going with proper track nuts. There's a reason they're called *track* nuts.