Focus Puller for Sony HDR-CX900

I wanted cheap and cheerful way of being able to pull preset focus depths on my Sony CX900 and came up with this. There are three pieces - an 'anchor' piece which sits in front of the focus ring (where it wont move) and two 'puller' pieces which sit on the focus ring.

Line up your two focal depths, holding the focal ring and sliding one of the two pullers to the appropriate position. Once set up you can go from your initial focus, to your second and third positions (the two pullers) - and the