Immediate verdict on hamster wheel #6: not large enough for a full-grown Syrian. I suspected it wasn't -- it's 6.5" instead of the usual 8". But they only have two sizes (the other is 12") and this is the one marketed for hamsters. I thought perhaps the central hub stick thing (must learn terminology to write proper reviews) was short enough not to cause problems, but Stella didn't like it one bit. Total elapsed time: approximately two minutes. I think I can probably return it for a refund.