Dan, Take a look at this page: http://konvas.org/faq/konvas-1m-2m-lens-mounts-oct-18-oct-19.html Basically, the diameter of the OCT19 is 68mm and the flange focal distance is 61mm. Cheers, Adam Frey Director/Cinematographer Crimson Chain Productions http://crimsonchain.com Crimson Chain Productions PO Box 35 Libertytown, MD 21771