Size 1 gallon, Mexican key lime (Citrus aurantifolia)
Key limes—also known as Mexican limes or West Indies limes—are small, spherical limes that grow in tropical and subtropical regions. They're light yellow (not green) when ripe and contain more seeds than regular limes. Their skin is also very thin, which means they don't store well.
Key lime trees are hardy in the U.S. Department of Agriculture zones 10 and 11, and they are sensitive to cold temperatures.