Saw it on this website. What is the prooduct ID? And is it able to work with Canon 350D and 300mm F/2.8L?

The Tamron 90mm macro lens may be used quite success-fully with any good quality teleconverter to increase image magnification or to increase working distance. In fact, I prefer to add a 2x teleconverter (Kenko MC-7 2x teleconverter) to the Tamron 90mm lens rather than purchase and carry a larger, heavier 180mm macro lens. I give up only one f. stop of maximum aperture compared to a 180mm macro lens and I still have a highly portable, handholdable macro lens. To the right is an image made with the 2x teleconverter attached to the Tamron lens. Very little sharpness is lost using a teleconverter on the Tamron lens. I do have a 1.4x teleconverter I will sometimes use but I seldom use it on the lens alone. Most of the time, when I want more image magnifi-cation, I want a lot of image magnification. Under these circumstances I will stack the 1.4x teleconverter on the 2x teleconverter for a 3x increase in image magnification.
Thanks in advance.