Fill a highball glass to the top with ice cubes
Pour 0.5 oz of lemon juice, 0.75 oz of grapefruit juice, 0.5 oz of Maraschino liqueur and 1.5 oz of gin into a shaker
Fill the shaker with ice cubes and shake
Strain into the highball glass
Top up with club soda and stir gently
Garnish with a grapefruit wedge