Concrete Screw Bits are used to pre drill hole used for self tapping concrete anchors and are specifically designed for use with TAPCON ®™ concrete screw anchors. When using self tapping concrete anchors, such as TAPCON ®™ concrete screw anchors, pre drilling the right size hole is critical. Make the hole too large and the self tapping concrete anchor screw will fail to achieve maximum holding power and possible fail to hold completely.