What are the different types of stem available on micrometer heads? The stem on a micrometer head is the main mounting feature and thus very important to the overall functioning of the device. Stems on micrometer heads can be plain type or clamp nut type and are typically made with an h6 tolerance for either a metric or imperial size. The plain stem is the most basic design and can be utilized in a wider range of applications than the clamp nut stem and is better for very slight positional adjustments in the axial direction on installation. The clamp nut stem is best for clamping micrometer heads in a fast and secure manner. One benefit of the clamp nut stem over the plain stem is that it does not require a split-fixture arrangement or adhesive for fixture. Depending on the particular measurement job you are completing you will want to make sure you have the proper stem type on your micrometer head.