Norton OHV valve springs, set of 4 ( 2 inner + 2 outer). Suits OHV models 1959+ Can be used on earlier modesl with change of collars. Length large spring 48mm diam 32mm ID 24mml length smallspring 44mm diam 24mm ID 18mm. Original part number: 21612 - valve spring inner 21613 - valve spring outer