The first "Search" window in the middle of the front page of the app allows you to search the data base by Numerical (caliber), by specific name (Alpha) or you can mix alpha-numeric.
Results that are displayed are for cartridges that include the information you entered. Select the result that is closest to your desired caliber, each result will show the gauges that are fully interchangeable with that result. If you do not see what you are looking for check the other options that appear in the result. If no result appears, it is likely that your caliber of choice does not interchange with any other caliber, I.E. it has caliber specific gauges.
Many gauges will have details (information) available that should be helpful in selecting the correct gauges for your desired use.
The second search method is to "Filter for Calibers"
Using this method you select the type or gauge you would be using according to case design. The Categories are very simple:
Belted Magnum Headspace Gauges
Rimless Bottleneck Headspace Gauges
Rimless Pistol Headspace Gauges
Rimmed Headspace Gauges
Rimfire Headspace Gauges
Select a category, Select Caliber, Select Product (narrower caliber selection); a compatible result will appear.
With either search method when your receive "Compatible Results" similar to the screen shot below:
Note that the list of "Gauges that Interchange" is a comma separated, continuous list.
The RENT or BUY buttons are used to place an order for the tools. You will be sent to the 4Drentals.com web site where you can order the tools you need.
Search as much as you like, its free and informative!