a shutoff device for shutting off liquids or gases comprises a device housing and a device movable in said housing , the device being provided with an opening . for sealing purposes , annular sealing bodies are provided which are supported in annular fluid cylinders . the contact surfaces are coated with a hard - material layer which is subjected to microfinishing . the sealing bodies are yieldingly supported such that they are capable of following any deformation or displacement of the device . the sealing is particularly suitable for aggressive and abrasive media and solids - carrying media .