Official rule text
21.8 Commodity tokens come in values of one and three. A player supply instead of a plastic piece. These tokens must be can swap between these tokens as necessary. accompanied by at least one plastic piece of the same type; players can swap infantry and fighter tokens for plastic RELATED TOPICS: Deals, Trade Goods, Transactions
View official source
Source: Twilight Imperium: Fourth Edition - Living Rules Reference: Prophecy of Kings
Expansion: Prophecy of Kings
Version: 2.0
Reference: Rule 21.8