The old, brittle plastic margin markers on my Olympia SG-1 broke.  Needed new ones, so I modeled these out.  They fit and work, but are very thin.  If you are printing in resin, be sure to mix in a good amount of flex resin, or you'll probably  just break them.  I filled in the intented markers using a red Sakura Pigma Micron PN pen.  It is not opaque like the original, but it stays on the plastic and is visible enough to see where your margins are.  I printed them flat on the bed, because trying to cut off supports broke them for me (but that was before I mixed in enough flex resin.)