As long as any of us have been reloading, we have been using comparators. These are simple items meant to let us measure seating depth and headspace between cases. If you reload alone, always use the same components and calibers, and don’t tinker around, these are a solid option. Really though, that’s not us. We like to use different components, we like to compare, and we want to know that the measurements we are taking are a little more than relative. This is why we are making our ZERO measurement gauges.