Quote Originally Posted by Lee L View Post
Here's a discussion that's pertinent and covers a number of focusing rail options: http://photo.net/bboard/q-and-a-fetch-msg?msg_id=000Zuq

I use the Bogen 3419 rail and like it a lot. It's low profile, packs easily in the top of a camera bag, and has a threaded rod drive for fine focus (1mm/turn?) with a quick release for fast larger movements. I mostly use mine on the small geared Bogen head with a QR plate, which is really nice for "dialing in" the composition and focus in macro work.

Your photonet reference does not correctly describe my RRS B150-B Macro Focusing Rail:

With my RRS focusing rail, Gross focusing and composition adjustments can be achieved by sliding the rail within the jaws of the clamp with a movement range of up to 128mm. Fine adjustment is made with the lead screw; the lead screw delivers 1.25mm of travel per full revolution. Total adjustment range is 231mm.

Of course, the RRS unit is compatible with all Arca Swiss type QR clamps.