I bought the watch as a birthday present for my husband. He teaches martial arts and needed a watch that could take more wear and tear.  The rubber helps keep the watch in place and he has not had any problems with it flying off his wrist when sparing. He has broken two other invictas becuase he forgets to take them off befor teaching.
I had a hard time finding a watch with a rubber band and a fold over clasp.  He doesnot like the bulkiness of a traditional watch band. Even though it has a fold over clasp you can fit the watch yourself.  You just pull out the pins.  However, you must cut the rubber down to the right size. So, if you gain wheight, there is no going back.