The ASTM E23 Charpy testing standard utilizes a striker of 2 ? 2.25mm radius, whilst the BS EN 148-1 testing standard utilizes a striker of either 2mm or 8mm radius. More energy will be absorbed by the 8mm striker for materials that measure high Charpy energy (approx. above 100J), compared to that of the 2mm striker.

Tests carried out with the 8mm striker will also report higher impact energy. At TWI, the specimens are tested on different machines calibrated to different agency reference standards, resulting in different outcomes even if both were to use the same striker and test specimen.