20 Lbs Mighty 109 Slate Flagstone Assorted Sizes 20 lbs of beautiful Mighty 109 Slate Flagstone. Assorted sizes ranging from 2 inches to 8 inches. Each piece averages approximately 1/2" thick. Stone has a range of tans, whites, greys, blues, browns, slates. Excellent for patios, walkways, stepping stones and adding accents to your landscape.