HCA: Hermit Crab Association

Hey guys Is it best to measure a shell that's closest to what they've got on or actually measure the opening of the shell they're in? All 4 of my crabbies have about the same size shell on which is a little odd because one is smaller then the middle 2 and the other is bigger then the middle 2. I think the problem is that I tried to get a variation of types of shells but they only want the green turbos that were in the sets?? Lol so I'm trying to get different colors and sizes in just turbos instead of getting the variety packs so I can actually tell who's who

Try to measure the shell they are in, even if you have to guesstimate. While openings are pretty standard on turbos (half of the total length of the shell), there can be slight variations of 1/8 inch or more between like sized shells.