28 mm Superseal Pipe Inserts for JG Speedfit Barrier Pipe. JG Speedfit Push-fit fittings are suitable for use with copper and plastic pipe but must not be used with stainless steel pipe. Fully inserted pipe inserts must be used on all installations with JG Speedfit cross-linked polyethylene (PEX) barrier pipe. The JG Speedfit range now incorporates push-fit and Twist and Lock fittings. They are suitable for most water supply systems, mains fed or indirect cold water, vented and unvented hot water systems and vented or sealed central heating systems (provided temperatures and pressures comply with BS 7291-1-2-3 Class S). NOTE : Where a fitting is suitable for central heating systems this is stated in the text below. JG Speedfit fittings and pipe are WRAS approved. Colour : white. PLEASE NOTE THAT THESE FITTINGS AND PIPES ARE for USE WITH WATER. Pipe inserts with ‘O’ ring to give extra seal inside the fitting. for use with JG Speedfit barrier pipe. Suitable for central heating systems.