My concinnus eat small pinkies and they aren't more than 13 inches, I get extra smalls in my boxes sometimes, but they prefer the larger ones. As a precaution, I would use the extra smalls, just in case Rune can't get the smalls down. My ordinoides, Runt, eats extra small pinkies when I find them, but can't eat a small one. She's about 13 inches too and about a year old.