I think you'll find that freewheels smaller than 15t fit on BMX flipflop hubs. The threaded side for smaller freewheels is thinner in diameter than a normal hub. This allows for a smaller internal diameter of the freewheel, hence a lower tooth count.
I think you'll find that freewheels smaller than 15t fit on BMX flipflop hubs. The threaded side for smaller freewheels is thinner in diameter than a normal hub. This allows for a smaller internal diameter of the freewheel, hence a lower tooth count.
They will not fit on a regular track hub.