Chaincase

A chaincase is a device that encloses the chain on a bicycle. It's a practical feature that is ubiquitous on bicycles ridden for transport in the Netherlands and Denmark. 

Chaincases prevent oil and grease from the chain from coming into contact with the rider, and their clothes. They also esnure that the chain itself is protected from the elements, keeping out rain and dirt, and reducing the need for maintenance.Chaincase