The flapper adapter is designed around a common centerline to insure high rpm accuracy when grinding or using precision carbide cutting burrs. The method of attachment has always been a simple 6" crescent wrench and an open end wrench. No special tool is required to tighten the collet nut. The adapter is made from stainless steel for additional corrosion resistance. The collet is made from tool steel and has been chemically treated for hardness enhancement and corossion resistance. Available in METRIC and STANDARD threads for a variety of world wide grindles and spindle threads, currently stocking M14 x 2.0, M12 x 1.75, and 5/8"-11 UNC thread. Nuts and collets are all interchangable with most standard air powered die grinders and end grinders. Our adapter comes with a lifetime guarentee against breakage and will be replaced upon presentation of the broken adapter at the buyers shipping expense to our address here in Oroville. Return shipping is pre-paid by us and you will receive a complete new adapter/nut & collet in return mail if our inspection reveals a failure due to our error in manufacturing. Cross threading and/or galled threads is NOT covered under this warranty, so be sure to use a tiny bit of "Never-Seize" on the threads initially so that the threads have sufficient lubrication to not gall.