If you can't find bottled Key lime juice (or fresh Key limes to squeeze for juice), just substitute 3/4 cup of the more common (and less potent) bottled Persian lime juice.
1 1/2 cups 1% low-fat milk
2/3 cup bottled Key lime juice
1/2 cup half-and-half
1/8 teaspoon salt
1 (14-ounce) can fat-free sweetened condensed milk
Lime wedges (optional)
How to Make It
Combine the first 5 ingredients in a medium bowl, stirring with a whisk. Pour mixture into the freezer can of an ice-cream freezer; freeze according to manufacturer's instructions. Spoon ice cream into a freezer-safe container; cover and freeze 1 hour or until firm. Garnish with lime wedges, if desired.