I've ordered this flash http://www.venuslens.net/product/macro-twin-flash-kx-800/ which I like the idea a of over over the slightly similar Adaptalux LED macro light because it's flash ( brighter and better motion stopping) and not a constant light source.But I see they also make variable length extension tubes for Canon EF and Nikon G mount lenses and bodies. Canon: http://www.venuslens.net/product/x-pro-vari-length-af-extension-tube-canon/Nikon: http://www.venuslens.net/product/xpro-macro-tube/I have no connection to the company or whoever is doing marketing for them but thought these products look promising enough to investigate
I would have liked to seen a tripod mount, especially for $169.
I see this as a good deal. A set of 3 fixed length tubes from Nikon is over $270, a similar set of 3 fixed length tubes from Kenco is $129, and a "Savage" variable length tube is $198, all from B&H. None of them have tripod mounts. A flat Arca style plate alone is over $50 from Kirk or RRS, so considering the complexity I'm surprised it's so cheap!