657-23503 ST1 Decarbon gasket set, Supersedes Part Number 657-23501. ComPac T24/33 this valve measures 1/2 inch

this valve measures 1/2 inch National pipe tread both inlet and outlet

This is the improved head gasket kit

This will be item 23 in the Lister Petter drawing

not questionable chinese knock offs

657-23503 ST1 Decarbon gasket set, Supersedes Part Number 657-23501. ComPac T24/33 this valve measures 1/2 inch657 23503 Lister Petter decarbon gasket set, former part number was 657 23501. This set is for a single cylinder ST model engine only. This set gives you the necessary gaskets to properly replace the cylinder head on a ST1 engine after removing the built up carbon. The ST model engine was used on numerous applications including generators, fan units, pumps and air compressors.