As I am working on my radio rack layouts I’d forgotten that the typical square punch out rack hardware can come in different sizes.
My Flex-6700s use a very thick rack mounting that would benefit with longer screws.
Commodity size and length seems to be M6 x 16mm and I ordered 20mm from the same product description online at Amazon, but didn’t realize that longer screws seem to be mostly M5 x 20mm rather than M6 sized.
The M5 seems to be a better match for installing audio gear and other items that seem to be just a little bit off of the spacing expected with a computer rack with square punch outs.
There is a SAE sized screw, but that seems most used in racks that have built-in threads, but of course they are available with cage nuts which makes it even more confusing.
Fortunately the cage nuts themselves often are marked, and the screws can be identified as thick M6 or thin M5 in the hand.
As the available suppliers to Amazon and eBay changed each time I looked to buy more I’m not going to include links. Rather a suggestion to search with “m6 rack screws and cage nuts” or “m5 rack screws and cage nuts” at either website.
After searching I did find the M6 x 20mm I wanted.