Clam sizing can confuse new buyers because the names — littleneck, topneck, cherrystone, chowder — actually refer to size classes of the same hard clam species, not different animals.
Hard clam size classes
Littleneck clams are the smallest market size, typically under 2 inches across, favored raw on the half shell or steamed whole. Topnecks run slightly larger, a middle ground between littleneck and cherrystone. Cherrystones are larger still, often used in linguine dishes or grilled. Chowder clams are the largest, tougher and best suited to chopping for chowder or stuffed clam preparations.
Soft-shell (steamer) clams
A different species entirely, soft-shell clams have a thin, brittle shell and a distinctive siphon, typically steamed and served with broth and drawn butter. They don't work raw on the half shell the way hard clams do.
Razor clams
Long, narrow-shelled clams less common on standard order sheets but growing in popularity for grilled or sautéed preparations, often imported or sourced from specific regional beds.
Ordering by count vs. by weight
Littlenecks and cherrystones are typically sold by count per bushel or bag, which makes portion costing straightforward for a raw bar menu. Chowder clams, often destined for chopped preparations, are more commonly sold by weight.
Storage note
All hard clam sizes hold similarly under refrigeration — 5–7 days at 33–40°F in a breathable container — but should never sit in standing fresh water, which will kill them before service.