I was about to suggest this: the joys of 'caged' bunnies is we can use their run to provide enrichment by hanging stuff off the top of it
Here's a video of them eating carrot strips:
https://www.facebook.com/keletkezes/videos/vb.199711564/10102245577747988/?type=3 And a bonus one of Lopsy with a cardboard tube (a proper thick one, not a looroll):
https://www.facebook.com/keletkezes/videos/vb.199711564/10101316823883178/?type=3. We can't give them tubes anymore because Aboleth gets all humpy as she thinks she's not getting her own way
I did get some thick PVC piping (the sort used for plumbing applications) that I cut down for Winter outdoor tube use, but never used it after Aboleth got all territorial
I'm forever telling the OH to watch it with fresh willow, but we've never had any issues and AFAIK both are generally healthy
Balls can last anything from a day to a couple of weeks depending on how mine are feeling!