I liked my original Jawbone UP24 however it broke and Jawbone replaced it with their new model the UP2. Newer means it should be better right? I would say different, but probably not better. My chief complaint with my UP2 was that it would not stay on my arm very well. The clasp was too easy to knock off when out doing things, even simple walking it seemed to come off for no reason. I was concerned with losing it so I went online looking for an answer. I ended up bending the clasp a bit to put some more pressure on it after seeing this post, this definitely helped but didn’t solve the problem. I then saw a suggestion on Reddit to use an O-ring. That post has disappeared from what I can tell now so I decided I would make a new one with new photos to show the fix. Since doing this my band has not fallen off once.
I went to the corner neighborhood hardware store into the plumbing section and found o-rings in the sink rebuild area. The o-ring cost me $0.49. The size I used was a #7 O-ring which is ½ x 3/8 x 1/16 in size.
You can put the O-Ring on the band or the clasp with similar performance. I hope this helps everyone fix their Jawbone UP2 bands.