instruction: What material is typically used for rowing shells?
context: Originally made from wood, shells are now almost always made from a composite material (usually a double skin of carbon-fiber reinforced plastic with a sandwich of honeycomb material) for strength and weight advantages. World Rowing rules specify minimum weights for each class of boat so that no individual team will gain a great advantage from the use of expensive materials or technology.
response: Rowing shells are now typically made from carbon-fiber.