Yes...They are sticky weights, like someone said.
I would however warn you about them. Alot of times they are very hard to get a good balance from them. I have used them but usually have to go back to my mech. several times for him to get it right.(Well not anymore but I did the first couple times he did them)
Just watch them do it, that way you know how close to 0 he is getting them?(on the machine that is)
Hope that helps,
Justin