5/8" Female DRILL (Small Threads) to 1-1/4" Male CORE BIT (Large Threads Adapter by BLUEROCK Tools Model #7 5/8" 11unc Female end fits 5/8" compatible drills 1-1/4" 7unc Male Threaded end fits BLUEROCK Wet type core bits as well as other compatible threaded coring bits. Solid all metal construction The 2.5" Core Bit is shown for scale and not included with this adapter. Please see our separate listing for core bits and core bit packages.