I bought these bands to use with Tony Horton's 10-Minute Trainer.  For the most part these are great until you have to do a military press or an overhead tricep curl.  These exercises require you to stand on the middle of the band and push all the way up until your arms are fully extended.  For these exercises, the bands are too short for me and I worry how long they'll last if I keep stretching them that far.  I'm 6'0" tall, so someone shorter might not have any problem.  If you're 6' or taller, I would find something longer because these will disappoint.  The B-Line bands used by Tony Horton for P90x and his other videos appear to be roughly twice as long as these.