I was looking for resistance bands to help with strength and conditioning for taekwondo.  These really fit my needs quite well since the package comes with a door attachment and ankle strap that allows me to train without a partner.  The tubes clip to the handles/ankle strap/door attachment with spring loaded clips rather than just sliding into some fitted slot, and they seem very secure.  I wasn't too sure I would like the metal clips at first, but they are very secure.  I've not seen the door attachment on other products, but this accessory is pretty slick, at least for my purposes.  Rather than attach to the doorknob or under the door, the attachment consists of a nylon strap with a ball inserted into one end.  The strap is then inserted between the door jamb and the door and is secured in place when you close the door.  What makes this work so well for me is that I can adjust the height of the anchor; low for kicking drills and higher for hand techniques.  The variety of tubing is also more useful than I thought.  I had anticipated needing only one heavy band for my training, but my 8 year old son and wife also like the bands and use lower resistance than I do.  All in all, a very neat little package for the price.