I saw them at one time but never purchased. Good product but limited run and high prices. They appear to have disappeared from the market.The LumaDyne fasteners have a face plate to them so you dont have to countersink the screw to the airframe. It has an aluminium flange to hold the countersink in the threaded part. Pem nuts are great but it's not what I'd choose to build with.
Ya, the height is the key. I've been able to find 1/8" height ones for some applications.Yeah, none of those are the same at all. The LumaDyne inserts are specially coated:
"The aluminum inserts are chemically coated with a patent pending treatment (CTXPPT treatment by Vindicoat, LLC. For more information regarding the latest advancements in conversion coating visit Vindicoat.com). This treatement changes the surface of the aluminum inserts so that epoxy will grab hold of the aluminum, and it becomes a permanent addition to your rocket. Without the special treatment, epoxy doesn't really grip the aluminum, and the inserts could pop out, like you may have experienced with some untreated aluminum conformal launch rail guides."
Also, (and probably more importantly) none of the others that turned up using that search are as short as the LumaDynes, they are all much taller. The LumaDynes are .09 inches, vs. about .25 inches for the others. I spent a good afternoon a while back trying to find something similar and could not, but maybe my Google-fu isn't that strong. The LumaDynes are essentially flush mount, nothing else I found came close.