Returkraft AS hereby invites tenderers to a competition for the delivery and installation of new filter bags at the annual maintenance stop at Returkraft facility, including taking out the existing (used) filter bags that shall be replaced. The contract will be valid for 1 (one) year, with an option for a further 3 years (1+1+1 year) if Returkraft AS so wishes. Parallel tenders will not be accepted in this competition. This means that tenderers shall only submit one tender in accordance with the requirements set by the Contracting Authority.