printing rollers , in particular ink rollers , dampening rollers or varnishing rollers for web - fed offset printing machines and sheet - fed offset printing machines , with a rigid roller core and a roller cover with an outside layer from elastomeric or elastic plastic material are constructed that way that the roller cover is connected with the roller core detachable . in this way for inking units , dampening units and varnishing units of printing machines rollers are made available , whose roller cover is exchangeable and can be used in a one - way method .