in fig7 c a set of side wall adaptor plates 23 can be used for reducing the width of the moulding chamber 2 from one standard width to another correspondingly two side wall adaptor plates 23 preferably of equal thickness are provided for installing on the chamber side walls 5 of the moulding chamber 2 the sides of the side wall adaptor plates 23 facing the mould to be produced are provided with side wall wear plates 16 mounted on the side wall adaptor plates 16 using conventional mounting means for the side wall wear plates 16 the mounting of the side wall adaptor plates 23 inside the moulding chamber 2 is preferably performed by using the mounting means for the side wall wear plates 16 for the moulding chamber 2 and this is made possible by removing the side wall wear plates 16 before inserting the side wall adaptor plates 23 in the embodiments illustrated in fig7 a 7c the height of the moulding chamber has also been reduced to the desired size furthermore in all of the embodiments schematically illustrated in fig7 a 7c the width has been reduced by the same size in both sides of the moulding chamber 2 this will give a more symmetrical application of the compression force on the pressure and swing plates 6 and 10 in general it will be preferred to provide a symmetrical change of width and also height of the produced.