This is the first version of the dfocus brand follow focus, with the additional marker plate added. The 2 lens rings are different diameters and slip over your lenses focus grip area and mesh with the large gear on the unit for focusing, and between the 2 should fit just about any lens you may want to use with this. I was using this with 2 canon FD lens, a 50mm and a 100mm in conjunction with a jag35pro DOF adapter which I sold, so dont need this unit anymore. I just put this up on ebay but it has a buy it now price of 85.00 plus free shipping. details on ebay here http://cgi.ebay.com/ws/eBayISAPI.dll...m=200488350485
you can also read more about this product here..http://www.dfocussystem.com/
you can also read more about this product here..http://www.dfocussystem.com/