Thread ring gauges are used to check the accuracy of an external thread. They have a threaded hole in the centre with three radial slots and a set screw to permit small adjustments.

A taper ring gauges are used to check both the accuracy and the outside diameter of a taper. Ring gauges often have scribed lines or a step ground on the small end to indicate the ‘Go’ and ‘No-Go’ dimensions.

Telescopic gauges are popular for fine work as they are very rigid and have a better 'feel'. Telescopic gauges are used for checking large internal diameters.

In the context of plug gauges, the "Go" side corresponds to the minimum acceptable size for the job or workpiece. The purpose of the "Go" gauge is to check whether the workpiece falls within the acceptable size range. If the workpiece fits into the "Go" side of the plug gauge, it indicates that its dimensions are within the specified minimum limits, and the part is acceptable.

On the other hand, the "No Go" side of the plug gauge is used to check whether the workpiece exceeds the maximum acceptable size. If the workpiece does not fit into the "No Go" side, it means that its dimensions are within the acceptable range.

So, to reiterate, the "Go" side of the plug gauge corresponds to the minimum size of the job, and if the workpiece passes this test, it is considered acceptable in terms of size.