A
Ana Rebeca
It is the 20cm one. I will build a new cage starting in a couple of weeks and I will sure try to find a bigger wheel then. I will also try to make it fit the bigger wheel as well as the same level substrate along the entire cage. For now, I couldn't even fit this smaller wheel on top of enough substrate, even though this was the biggest cage I could find in any petshop in this cityAlso I can't tell if it's a 20" wheel or a 28cm wheel, but it looks like it may be the 20cm one? That size is fine initially but they do need a larger 28cm one when they start to grow and that might mean the need for a cage upgrade, to fit one in. It's very difficult when you want to fit more in - I had the same issue with my robos cage set up recently. I wanted to fit a lot more in but there wasn't the space to do so and he is in a 100cm x 50cm cage - but I have some large items in there. If one of the dig boxes has sand in and the other has a different substrate, you could maybe lose the one nearest the edge of the cage and just scatter the other substrate. Add a few treats to it for him to forage for so he doesn't get upset by losing the box! It will give him a bit more space to roam around in that area
Most cages are not ideal to set up! They can be too tall or not tall enough to achieve everything.

The box in the corner is the sand bath, while the other one is just a diy multi-chamber made of cardboard until I can get him a proper one. I wanted to scatter some bark chips in the lower level but I found out they were pine chips and I read that they could be harmful, so I will have to find other chips.
Thank you very much for the advice! <3