7.5 oz. Cointreau
2.5 oz. fresh lime juice, fine strained
15 oz. fresh grapefruit juice, fine-strained
6.25 oz. filtered water

Method: Prepare batch in a large container and funnel into a siphon. Charge with CO2 and keep on ice or in a refrigerator. Serve over ice in a tall glass. Garnish with a grapefruit twist.