These felts are 100% wool and are suitable for printing etchings on the plastic press. 
 
sizing catcher: The thinnest of the felts, this felt should be the one contacting your paper when you print. This felt will absorb the paper sizing that is released when you wet your paper and prevent it from stiffening your cushion felt. Over time this felt will become stiff from absorbing a lot of paper sizing, simply hand wash the felt in a tub of cool water and gently hang it dry. The felt will become soft again. 
cushion: The thickest and softest of the felts, this felt should be in between the sizing catcher and pusher felt. This felt provides the depth and softness to push your printing paper deep into the grooves of your etching. 
pusher: This felt is the densest and toughest of the felts and sits between the cushion felt and top roller. The purpose of this felt is to protect the delicate cushion felt from the scratchy friction of the roller drum. 
 
To print etchings with these felts I recommend raising your top roller higher than your intaglio matrix, then lowering it until it just barely does not touch your matrix. This will be a good starting printing height. Raise your top roller 2 revolutions and then slide your press bed with felts in the press. Once your press bed and felts are caught between the rollers, go ahead and lower the top roller by two revolutions. While printing I recommend NOT letting the press bed travel all the way through the press, and instead leaving one end of the felts trapped under the roller in between prints. Do not leave the felts sandwiched between the rollers for extended periods of time when you are not printing. This could lead to permanent deformation of the felts.