These pulleys are for the 1/40 scale Anfora kit Duna (actually the Fredeeric Mistral) amd connect the ship's wheel to the rudder. They are placed along the deck sides and allow the chain to run through them. The chain can be no larger then .085 across the links. There are 24 pulleys which allows for a lot of spares. The sheeve turns free.
Can be used for other models as well.