Two things: they are remarkably active and need lots of room to roam. So if that is his night time/inclement weather enclosure it might be okay...but it's small otherwise. Secondly. ..the Russians are really good climbers so you have to make sure he can't get over the sides... anywhere in the enclosure. You probably need 15".
I have a Hermann's. ..but care for the Russians/Horsfield's is more or less identical.
i agree with rue the sides look a bit short for a 10yo Russian and it does look a bit small for a long term enclosure. also what are you using for substrate? keep in mind they love to dig
It's 8x4 but I will also have an outside area in my yard. I will make the sides taller as well. Getting him from a friends dad who can no longer care for him. Substrate is coco core, moss, and cypress mulch.