ive owned a al-pd, ti-pd, ti pd-s, and a ti s27, out of all of them the most useable was the ti pd-s, but i would have loved it just the same in aluminium. the 20mm reflector is great for what those lights are driven at (25/525ma) that light isnt bright enough to make use of the 27mm reflector, and also it makes the light a tad awkward, whereas the pd-s is pretty much the perfect size, also the surefire beamshapers fit it perfectly, get an F04 and keep the pd-s.