Okay.  So I have had these resistance bands for little over a month now and am really pleased with them.  The main thing I like about them is that they are so easy to configure due to the carabiner connectors.  While I am not a materials engineer the quality of the bands and the various components is good.  The stitching on the ankle and door bits is good.  I had no problem using the door attachment.  It slid right into the space between the door and frame.  I closed the door and was working out within minutes, once I got the right level of resistance I was looking for.  Need more just add another band.  Need to reduce the resistance just swap out or reduce the number of bands you have attached.  Easy as pie.