Unlike old fashioned plug type anchors, Alligator anchors mold into the imperfections of the hole for superior holding power, and the anchor stays in place when the fastener is removed. Alligators work great with a wide range of sizes, and in a wide range of materials, so selection is easy. For maximum grip in dense materials (concrete for instance), use the same size screw or lag bolt as the pilot drill! In brick or softer masonry, use a screw in the middle of the range; for drywall or very soft materials, tend toward the low end of the range. Can be used in hollow walls or solid materials. Box quantity includes 200 anchors only. Screw Range #4 - #10. Made in USA.