what can they chew on

My 5 cheeky monkeys are all getting baby teeth. They seem to have front and canine teeth.
They are chewing on the opening of their cardboard box and other boxes I have around the house for my other cat and momma.
I have taken care of any wires so they can't chew them but I'm wondering if there's something I can give them to chew on.

My kittens also chew on cardboard, I doubt it'll hurt them. I also get some foil and ball it up and they play with/carry it around/chew on it a little, and they seem to enjoy it.

Layla has become quite the little chew monster lately. We gave her a small little stuffed bear for her to play with. It's almost as big as she is, and she'll wrapped herself around it, and do the "jack rabbit" kick to it constantly. I would just recommend buying them toy's and such, stuff to keep them entertained, so they won't chew on boxes.

I will say though, I couldn't imagine just letting my cat's play with a foil ball, especially if they are chewing things. If they get a piece of the foil, and chew it, and swallow it, it would tear their insides. I assume this is the same reason most people won't use tinsel on Christmas trees, it's the same concept. Just something to think about...

My kittens don't sit there concentratingly chewing on the foil ball. When I made the foil balls, I wrapped them so the ends are toward the center and unreachable. So far the balls are fine, nothing has happened, just a lot of batting them around.