For a tall 16oz glass: prepare glass with 2-3 cubes ice then add the chilled Gin (two shots). Next, juice and strain grapefruit (add grapefruit juice to glass). Fill remainder of glass with tonic water and gently stir. Drink will be pink and delicious! (Adjust to taste/preferred level of drunkness.)

Note: One half of a fresh large red grapefruit should be enough per glass.

This is a favorite in my house, enjoy!
P.S. Yes this is basically a Vodka Greyhound with gin, but it's better this way.