This tube fits between the lens and the camera body and allows for closer focusing by extending the lens. The 67mm tube has a fairly large effect at bringing in the close focus range of a lens, but will have a noticeable drop in exposure value. Most commonly I will fit this tube to the macro lenses to be able to get in very close for high magnification. As a special application, this tube also accepts the 150mm APO Macro bellows lens and allows it to focus to infinity.
Tubes and extenders can be stacked to get more extension. 9mm, 17mm, 34mm, and 67mm tubes are offered plus a vario extension tube with 22-68mm range and the extension bellows which can extend from 67mm to 204mm.
Note: I have two new ones left in inventory in original sealed boxes. Price greatly reduced from original list of over $700