Very good product. Have used it before a few times. Of course not sure how accurate it is, but it does the job and it gives you a vague idea. For the price i would say it is a bit much. Should actually be sold for no more than £30 in my opinion just because you do not really know the validity of the results. Is there a way of finding out how accurate the product is and who (sports athletes) or the like use it. This would be useful.