Why are all trading pairs displayed as XXX-USD in the Unified USD Orderbook? For simplicity and clarity, all trading pairs in the Unified USD orderbook are displayed as XXX-USD. This unified representation eliminates confusion about which stablecoin is being used while keeping the focus on the trading asset.5. Are there any additional fees for using a specific stablecoin in the Unified USD Orderbook? No additional fees are applied based on your choice of stablecoin.