This European Standard is applicable to uncoated cylindrical steel sheaths with a corrugated profile and with a nominal internal diameter of up to 130 mm and their connectors (couplers) which are assembled to form ducts for prestressing tendons in post-tensioned prestressed concrete structures. It is only applicable to sheaths and connectors made of interlocked or welded steel strip 1) . It does not cover plastic sheaths 2) . The seals required between sheaths and couplers are not covered by this standard. 1) In case of coated or galvanised steel additional requirements should be considered, which are not covered by this standard. Additional requirements may conform to the relevant provisions in the place of use of the product. 2) For plastic sheaths, see annex A.