What is direct gaging and how is a ring gage involved? The process of direct gaging is when a ring gage is utilized as a means of checking the size and/or roundness of a part. When conducting direct gaging, the ring gage can either be a go ring gage or a no-go ring gage, sometimes known as a not-go ring gage. Direct gaging, or fixed-limit gaging works to establish a physical limit for the acceptable outer diameter of a part. Depending on the high limit (go gage) or low limit (no-go gage), it can be determined whether the part is oversized, undersized, or within an acceptable limit. Additionally, direct gaging is useful for testing the roundness of a part that might be missed when using a micrometer or some other tool as a comparator.