Strangely enough Gizmo is actually quite a bit larger than Ozzy (they are both within the recommended weight for male dwarf hamsters) I believe this is due to the fact that Ozzy is a lot more active than Gizmo (Ozzy is up for about 10 hours every night, whereas Gizmo is up for about 7). They have 2 of everything apart from the sand bath, but I will try and get them another one. Thank you for the help and advice everyone!