I love these extensions, I bought 2 because they have clasps on the end of the drill motor so they can be stacked. The mount is important because with some good locktite on the set screw and safety tape around the set screw they will not loosen or come apart. If they break up, you've just lost a $30 drill. The packaging was also good and was sent with UPS, so that you could always track where the package was. I'm glad they didn't send via Smartpost.