3 ms·The micrometers (you need one for every 25mm, e.g. 0-25mm, 25-50mm, 50-75mm, etc. is very interesting!).by quickthrower2 3y agoThe micrometers (you need one for every 25mm, e.g. 0-25mm, 25-50mm, 50-75mm, etc. is very interesting!).