Very good product for the price.  It holds up well, and provides the resistance claimed.  You do need to pull it to the maximum to get the full resistance level.  The good part of this product is that those who need "less" resistance can use this , and then work up to the higher levels.  The instructions don't mention that.  This is really good when you have only a few minutes at a time.  5 minutes here and there adds up.  I recommend this highly.  The reason I don't give it a five is the door jamb piece.  I am not sure I can trust that.  I use large eye bolts that I screwed into the studs in the garage.  Those are very solid with no chance of slipping loose.