The bellows described in this specification are manufactured from PTFE, as detailed in product specification. The reinforcing rings are Stainless Steel. Flanges are drilled and taspped to conform to either ANSI 150 or DIN drilling and are painted with a corrosion resistant red oxide primer before despatch. The convolutions are contour moulded to uniform radii, free from sharp corners and other areas of stress concentration. The gasket face of the bellows is concentric with the bore and conforms to the appropriate flange raised face diameter for the equivalent pipe size. The flange assemblies are equipped with limit bolts to restrict extention to within the prescribed limits. For sizes 300 NB and above only two limits bolts 180 deg apart are fitted. All assemblies have their gasket faces protected by end plates, which are not to be removed except for inspection, testing, or installation.