Apple had said that the sport band, available for the Apple Watch, comes in two sizes: S/M and M/L. This led people to think that there were two bands in the package. This led at least one person to set up a website where people could swap their extra bands.
This is not the case, however, and Apple has updated the way they present the Apple Watch sport band, on their online store, to reflect this. The Apple Watch Sport page now says the following:
Essentially, one side of the band is a fixed size – presumably the one with the aluminum button – and the other side comes in two lengths, so you can get the right fit.
This will disappoint the person who thought they’d make a business out of being a middleman for Sport band swappers, but that’s life.