The item appears to be of top quality, it works well in the Wii Mote, but it comes with a fatal flaw.....
When using the battery packs you can no longer use accessories such as the Mario Kart Weel, the baseball bats, tennis bats, the light guns for any shoot em up games. It's also problem-matic with the Motion Plus.
Essentially this batter pack adds two prongs at the bottom or the remote, thus extending it and preventing anything going on the end, or it slotting into anything.
Ruins the Wii experience.
If your not bothered about all those extras, then by all means this does seem good value for money.