This is a churn used to make Tibetan butter tea. They are traditionally made of wood, though some are made of plastic these days. To make this tea, you should break a handful of tealeaf bricks called chapaka, and decoct them in a large pan for about an hour. Then you add a large paddle-full of yak butter from a dhi ‘female yak’, and a large spoon-full of salt, churning the mixture in the cylinder. Although the churning rod is effectively designed with a slit valve at the lower end, pumping the rod up and down dozens of times requires great energy.