While you are on the site, in your browser find and click "Add to Home Screen" A CGN beaver app icon will then be created to your phone that is directly link to the site.
Note: This feature may not be available in some browsers.
Kev, what head style do you need? Filister (bottom of head is flat)? Socket Weaver oval (countersunk)? And what length? I'm guessing 1/4" if it's for a scope base.
Use a dial caliper or micrometer to see if it is .164" (#8) diameter, and check the pitch with a thread gauge to see if it is 40...that's how I'd do it.