Mostly aesthetics but also functional these are Customized Cine Lens Housings by Cinematics that are designed to fit over existing Canon, Nikon, and Zeiss Lenses. We had an early look at these during PMA 2012 earlier this year, and the build quality is pretty amazing. Example below shows a basic Canon 50mm F/1.4 next to a modified 50mm F/1.4 in a Cinematics Custom Housing.
Cinematics Custom Cine Lens Housings
The customized housings have clear markings, and provide built in aperture and focus lens gears with an increased diameter that should make focus pulls longer and smoother. Some of these lenses have also been modified with a de-clicked aperture, a common feature found in cine-style lenses.
Prices vary depending on which lens has been modified into the custom housings and can be found via eBay (Click Here).
Cinematics Customized Cinema Lens Housing