Edmund Optics #39-729 PINHOLE 500 micron stainless steel (MOUNTED) + #38-534 pinhole adapter Description: these were found in my lab. SPECS: 500 micron Ø Stainless Steel Ø 9.5mm, centered to 50 micron tolerance and diameter tolerance 5 micron. Thickness: 0.02mm (0.001"). Mounted in a Ø 16mm metal adapter (Edmund #38-534), which in turn is mounted on a protective square plastic mount 2x2" (51x51mm), which in turn is presented in the plastic container bag you see in pics. It must be removed from plastic mount in order to use it, so you need a mount that holds Ø 16mm or else to unmount the pinhole from adapter (very easy to do). Condition: almost no use in opened bag. I saw pinhole through my microscope and it is nice, perfectly round with no damage. Guaranteed.