This spring I was replacing my heater core along with the entire cooling system on my 04 tj. Since the performance radiator heater core was out of stock at the time, I went with spectra. Now that it's getting cold out again, it's obvious that the spectra does not work nearly as well as the OEM core did. As mentioned in another thread, the thick plastic turbulator in the spectra significantly blocks the flow. The spectra works well enough to keep the cab "warm" when it's cold outside, but I miss how hot the original was before it exploded haha. You would nearly burn your hand holding it in front of the vent. I can also confirm that the spectra doesnt leak, so if you live in a mild climate then maybe that is the one to get. I, however, will be swapping in the heater core from performance radiator, now that it is back in stock.