How do i know what size pinkies i need to order from rodentpro.com?

my snake eats the pinkies that i buy from petsmart. they are the only pinkies they have and the box says 11 grams and 4oz. I am confused because there are extra small, small, and large sized on rodent pro and the grams dont match at all. I dont want to purchase a 100 and them to be the wrong size