Enn49 to the rescue!I use them for 2 of my Ts but have just left them with the screen tops. A 15.5cm square should just sit in the top over the screen. If you are taking the screen top out it would need to be an 18 cm square.
If they are the little ones that you said you ordered then an ExoTerra Nano will be too big. 1/4"-1/2" I keep in a vial and at 3/4" a 3'' cube is ideal but I keep my little ones containers inside an ExoTerra for added security as I have cats that just love the crickets. To be honest you'd never find them in a Nano at that size. I've just moved my P. metallica into a Nano and it's 3'' now and I have a job finding it sometimes.
Another reason to buy more T's lol
There is a reptile show about 3 hours from me this weekend, ill probably go out there and see if I can buy any smaller enclosures before I order more
Gifts to oneself are the best kind. [emoji4]It's father's day so I'm hoping to buy a present or two, to me from me. lol