This document specifies: – materials; – design requirements; – specified values for resistances and stiffnesses which a coupler has to achieve under test; – test procedures and assessment; for the following special couplers: – screw or wedge half couplers, sleeve couplers with shear studs, right angle reduction couplers and swivel reduction couplers. It gives recommendations for ongoing production control. These couplers are for use principally in temporary works. Each coupler is able to be fixed to at least one side to one 48,3 mm diameter steel or aluminium tube. For the other side of reduction couplers, this document specifies requirements for the diameter and wall thickness of tubes. Other special half couplers such as half couplers attached by riveting, used mainly for prefabricated members of scaffolds, are outside the scope of this document. NOTE – Information on design using special couplers is given in Annex B.