Scaffolding Girder Coupler Standard couplers are widely used with Ø48.3 steel scaffold tubes, we also produce a few number of special size couplers to suite with different diameter scaffold tubes, such as 34, 38, 60, 63 and 76mm. Also some special couplers are used for special functions, such as spigot support, deck retainer, toe board fixing, ladder bracket and so on.