A plastic spacer that presses the sail's luff profile firmly onto the mast and holds its shape regardless of wind pressure. Race sails usually run four, at roughly 5 to 9.5 square metres.
The difference isn't marketing: a no-cam sail flips its profile back and forth with the wind pressure, a cambered sail keeps it. On a relaxed freeride session that flipping doesn't matter; in a race in gusts from 30 knots up, a fluttering profile costs real speed. The most common mistake is rigging a cambered sail like a no-cam one: each camber has to be levered over the mast individually until it clicks in, and forcing it damages both the spacer and the cloth. Budget twice the rigging time. Mistake two: trimming too soft because it feels nicer when you uphaul — race sails want a tighter foot, otherwise the profile gets too deep at top speed and slows you down. What often gets missed: cambers are mechanically more fragile than a plain batten system. Rinse salt and sand out of the camber cups after every session, or the whole thing snags mid-gybe.