This is the M0CVO Antennas Magituner.  If you want a short wire antenna or a short wire vertical (run up a fishing pole or similar) then this is the unit you will require at the feedpoint.  The wire can be any length you want but should avoid being of a resonant length of any of the desired frequencies.  Basically, a length of wire between 7 and 8m  should get you on all bands from 40 - 6m via any ATU (including your radio's internal one) and a slightly longer length (10 - 11m) should get you on all bands from 80m - 6m via your ATU.  Maximum power handling 400W.