Eee! So tiny! How cute! And yikes, it's a good thing your cat didn't think they were prey. That's so funny that she tried to herd them. *dies* I can just picture it.

About as big as my fist? I have smallish hands, so that's not very big. He seems inclined to keep his body scrunched up, and didn't stretch out even when he was hopping around, so it's difficult to tell.