Waaaayyyyy smaller than Littlenecks which are actually big clams despite the name. Cockles are another bivalve of the same family. At least in my opinion, the smaller the clam the better the flavor.

I've seen really small Littlenecks or Manila clams labeled as 'cockles' at the fish shop, but actual cockles have vertical ridges on their shells. They're tiny, briny and delicious with pasta - I often find them at the Asian fish shop.

Cockles are a type of clam, typically smaller than littlenecks.