I first discovered these drive guides as part of a deck building pack offered by a local home center.  That was at least eight years ago and I have been using these ever since.  They do what they are designed to do - allow you to drive screws one handed.  I have had great success driving every length of screw up to and including 4" with this driver and my 9.6V DeWalt cordless drill.  I have never worn one of these out while using it for its designed purpose, but when I used it in a pinch to drive hundreds of metal barn siding fasteners (I removed the bit and was using the guide as a socket drive) the end mushroomed out and lost its shape.