Puzzle

A boy gets to work for a local shop-keeper. He was asked a question by shop-keeper for which you have to give answer. The question:

Tell 4 such weights (Baat like 5 Kg., 1,2, 10 Kg. etc.) without the restriction of being in vogue or not (means u can tell even 6 or 7 or 8 Kg also but not in decimal) so that I am able to weigh any quantity (again not in decimal) from and including 1 Kg to 40 Kgs.