The DL type impact device of Mitech portable hardness tester, height 204mm, weight 50g, diameter 20mm, has build-in DL impact body, front side is slim device, it is suitable for hardness measurement of the narrow parts (like holes, slits) of the workpiece with weight above 5kg, thickness above 5mm. It is widely used for the narrow part of the installed machinery or permanently assembled parts, rapidly testing for multiple measuring parts in large range of the large-scale workpiece, hardness testing for gear tooth root and other slender narrow grooves or hole. It can realize the precise measurements for Leeb, Brinell, Rockwell and others.