Kenko extension tubes available

Question for Jerry, since you already have a set of the Kenko tubes: I have a set of non-wired Chinese OEM tubes, and my problem with them is that the least possible extension is often more than I need.

In other words, I can shoot at normal distances with the lens alone, or nearly 1:1 with the thinnest extension tube... but photography of smallish but not tiny objects falls into the gap between these ranges, and there's no way to get there.

Is the Kenko tube thin enough to allow focusing at slightly longer ranges? Most of my close-up photography subjects are such things as electronic circuits that might be in the range of 2 inches to 6 inches on a side.