I bought one of these http://www.ebay.co.uk/itm/8-SIDED-METAL-DOG-PUPPY-RABBIT-PET-PLAY-PEN-RUN-5-SIZES-SMALL-MEDIUM-EXTRA-LARGE-/380452005764?pt=UK_Pet_Supplies_Dogs&var=&hash=item5894b4e784 for my 4 week old hand reared baby as her box is getting too small and she wants to run around...