Hmmm mine were 1 piece (well, 1 poly piece, 1 steel insert). I have never used the eccentric ones, or adjustable so perhaps they do something. The poly ones I guess made a LITTLE difference. Unless you are already in there and have the subframe off, it is probably not worth the work if you are just upgrading. If you have blown stock rubber ones, you COULD get poly ones to make installation easier.