Bitter Cosmopolitan Punch

2 cup grapefruit vodka
1 cup orange curaçao
¾ cup fresh-squeezed lime juice (about 4-6 limes)
1⅓ cup cranberry juice
⅓ cup fresh grapefruit juice (about 1 grapefruit)
a Tsp orange bitters
4 grapefruit slices for garnish

Add all the ingredients to a large punch bowl filled with ice and stir gently to mix.