Difference between S584113X300 and 584113X300

So it's come time to buy new brakes and rotors and I see sellers on eBay hawking part S584113X300. What's the S at the beginning denote?

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Not sure if there is a difference. It may denote semi-metallic pads, but that is just a guess. Could mean they are made in the Seoul plant too. Maybe you can ask the parts guy at a Hyundai dealer.
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I'm thinking you're on to something with the Semi Metallic. Next time I stop into the dealer I'll ask.
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