How do tennis balls work when drying a down comforter?

Question

I was just reading a question on how to make your down comforter all fluffy again and almost all the answers said that you can put some tennis balls in the dryer to make that happen. So how does that work exactly? Why does this happen? Can you use something else rather than tennis balls? Thank you!

Ami

Answer 1

I use clean sneakers.  I think they work better.

Answer 2

The tennis balls bounce around the dryer and keep the comforter from bunching up. This prevents lumps from forming with the feathers and keeps the comforter fluffy.