Bests & Worsts Reviews from Amazon

I think I got a dud. Lots of people seem to like theirs, but mine never gets the same reading twice. When I weighed myself with and without my suitcase to count the difference (the mostly infallible old-school way) I got the same number every time, versus when I used this device three times in a row, I got a different number each time - and I tried this trick with several different objects (suitcases, duffle bags, hand weights, purses, shoes, etc...). This thing just sucks.