Must be softball bats.  10U requires the ASA/USSSA stamp so you may want to purchase with the future in mind.

Choosing a bat - I have come to find that most kids (including my own) are using bats that are either too long or too heavy, this helps explain that if you are in the market for a new bat: https://www.youtube.com/watch?v=OKMrpfQJyuo