No idea... but perhaps that's why some owners experienced difficulties with certain bulbs. The ballasts are interchangeable and easy to install and plug. Routing the bulb cable in and out of the headlight assembly is a pain, but not impossible.
I'm going to play it safe and and use the "old" ballast to match it up with the new bulbs (5000K Morimoto). TRS did revise the bulbs to make them work with the new ballasts, though.
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