Is there any fabric that can be harmful to my plastic yoyos? I figured it wouldn’t but I wanted to make sure.

Off the top of my head, I can’t think of any fabrics that would be harmful to plastics or metals.

I think maybe if the forum knew what your intended purpose is, it might be a little more useful in order to better answer your question

i don’t think so.

I couldn’t find any foam so I was going to lay it on the bottom of my storage box because I thought it would be less likely to scratch my throws.

You’ll be fine unless you have some glass shard acid covered forever flaming fabric.

If you’re going to lay something down, lay some thick felt down and glue it down using a fabric glue. The felt is thick enough to provide some very MINIMAL and basic padding, and it’s often not super slippery. A couple of layers of that should work fine if you’re also carrying the case around. Comes in many colors at many retailers, including Wal-Mart. Not too expensive either.

Okay that’s a good idea I have some felt and fabric remnants.