0.3mm pinhole aperture mounted in a extra large 1 3/4 holder or 44.5mm in diameter. This is the perfect size for wide angle large format cameras with a short focal distance. If you require a different size holder they are available upon request   
This pinhole is precision laserdrilled then mounted into an aluminum holder is 0.6mm thick and the pinhole is 0.05mm or only .002 of an inch thick. These pinholes are outstanding and unrivaled quality due to the thinness of the pinhole and the perfect forming of the aperture using the most advanced methods. 
Most people will mount these in a camera body cap, digital or film. This is also the ideal size for SLR cameras. You could also build your own camera around this pinhole out of something as simple as a cardboard box.
These are scientific grade apertures and have been utilized by universities and laboratories. The second photo shows the pinhole at 800x under the microscope.