Mitutoyo Surface Roughness Detector Extension Rod - 50mm This Extension Rod is designed for use with the Mitutoyo Surface Roughness Tester models SJ-411 & SJ-412. The Extension Rod is 50mm in length, giving you extra length with your Mitutoyo Surftests to measure the surface roughness on hard to reach applications. The Mitutoyo Surface Roughness Tester model SJ-411 is available in 2 different models, the Standard Force model and the Low Force model. The Standard Force model uses 4mN measuring force during the measurement. The Low Force model uses 0.75mN measuring force during the measurement. This Detector Extension Rod for the Mitutoyo Surface Roughness Tester model SJ-411 works with Both Force models of the SJ-411. Features include... 50mm in Length