With this distance-kit it is possible to vary the hight of "TEC-HRO system 2.0", the sight-enlongation "TEC-HRO extender" or  "TEC-HRO system Auflage" any old from 11 - 31mm in always 2mm-steps.Consequently you can find out the optimal position of your head in every position (prone, standing, kneeling and also in the German discipline "Aufgelegt") and calibrate them.Advantage of this distance-kit is also, that you only need ONE sight-elevation, which you can adapt fastly and exact (just in 3-position-match) and use for the next position !!