I agree that the testing strength is probably different for each company. The fluoro that I looked at was Seaguar, and the comparable tests (the only basis for valid diameter comparison I believe) and the seaguar was noticably thicker in diameter than the tippet material. IMHO, since tippet diameter is directly correlated by the size of the fly, I will use fluoro for all my small dries (18 and smaller) since the weight of the fluoro seems to have no effect on the floatability, but I like that it sometimes breaks the surface tension which does away with those "awful" shadows caused by the surface tension around my floating leader. As a last thought, there is no reason why an individual could not buy seaguar 4 lb and use it as 2x (again estimating as I have none in my hands) and still save money, but a flyfisher would have to mic the seaguar to get a good idea of where it fits into ther tippet arsenal.