Tennis Balls

What do you guys throw with in the winter? Is it ok to throw tennis balls? I know there really light, but i don’t really have anything else. I throw in my basement which is about 45 feet long. Is there anything else i could use, or are they ok?

no you can throw out your arm with tennis balls try to buy pastic covered soft trainig baseballs the ones that they use for tea ball

Yeah, but won’t them get lopsided? I throw against a brick wall. I might be able to hang up a blanket or something though.