Uh, all rebuilds are from OEM cores.
That's a marketing claim we take on face value too often. In my experience with several of those for Land Cruisers, they were cheap castings from a Chicom molds knock-offs. one was not even fitting right. Tried a few times: correct casting numbers and all that, but you could see a horrible metallurgy from a mile. Some boots were dislocated, some were not polished, etc. Various 'brands', including the ones that swear they use OE cores.
Just a warning. NAPA Eclipse line was OK. Or a rebuild from a dealer is a second best choice aside from a new one.
Deal locally only. I made a mistake ordering from Rock once. Was stuck with a wrong part and it took a week of emailing back and forth with pictures and measurements to prove that the part was defective. The same happened once with a defective/wrong rotor: correct part number with a wrong hat height dimensions. One out of four was wrong and it had scuff marks from a previous customer also trying to fit the wrong part on his vehicle.