What material is typically used for rowing shells?
Below is an instruction that describes a task, paired with an input that provides further context. Write a response that appropriately completes the request.

### Instruction:
What material is typically used for rowing shells?

### Input:
Originally made from wood, shells are now almost always made from a composite material (usually a double skin of carbon-fiber reinforced plastic with a sandwich of honeycomb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:

Originally made from wood, shells are now almost always made from a composite material (usually a double skin of carbon-fiber reinforced plastic with a sandwich of honeycomb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.
Rowing shells are now typically made from carbon-fiber.