If you want to move your Pioneer Power Meter from one bike to another, you'll either need to move the magnets that turn on the meter or purchase a second set of magnets. The Replacement Power Meter Magnet Set is that second set.
It comes with both the patch-type sticker magnets and the arm-tip zip-tie magnets. You might be tempted to think that you can use either on any bike. That isn't necessarily true. If you're reading this, you probably have a Pioneer Power Meter already, and can certainly try the unused set of magnets that came with the meter on your second bike. But chances are, that both won't work, just one set will, and this comes with one set of each so you're covered no matter what your second bike needs.
The Pioneer Replacement Power Meter Magnet Set turns your second bike on to power.