From Citizen Sleeper Wiki
Clubhead Caps are items players encounter throughout gameplay of Citizen Sleeper.
Description[edit]
Clubhead Caps are small, strange-looking items found aboard the Eye. They are useful for players wishing to complete Riko's questline. After completing the Fruiting Bodies clock, players must provide Riko with 3 Clubhead Caps which will in turn complete the Clubhead Analysis clock.