I picked this up via Cinescopophillia on Twitter. It looks like this may be one of the first optical Canon EF to PL (positive lock) mount adapters ever made. There are many mechanical EF to PL adapters on the market that have a very limited PL lens range. The mechanical adapters are great because they do not require any modification of the camera. The Zunow optical EF to PL adapter will also mount to any EF adapter. The question here is, will it work with all PL mount primes? Most PL primes will protrude into the body and hit the shutter. That is why some type of modification is typically necessary. I have emailed the company and will update when I get a response. The Zunow EF to PL adapter is not cheap. It will set you back over $3K US. Click here for more info.