This is a wire strain gauge suitable for measuring the average strain of concrete under testing.
Typically, for this purpose, models are selected where the gauge length is at least three times longer than the maximum diameter of the aggregate (gravel, sand, etc.).

KC-60-120-A1-11 / KC-70-120-A1-11 / KC-80-120-A1-11 / KC-120-120-A1-11