I bought these from Hoop Dance Co. and was rather disappointed. They are really sloppy. None of them is as resistant as the one that came free with Yogalates energizer, which, by the way I found far too strong. I think they are probably intended for people recovering from injury and the white writing on one side 'physiosupplies' - which is not shown in the picture - would tend to reinforce that idea. You could use two together, but I still think they are not made of a stable enough form of rubber. The resistance is light at first but then rebounds drunkenly, causing overbalancing, rather than the firm and steady increase of difficulty I was expecting. As a taiji master said "The gentle always overcome the mighty." Well this gentle person would at least like to get toned trying.