I meant One S and One X, plus Series X. The One S and One X are refreshes of the One, with the One S getting 4K HDMI and Blu-ray support and the One X getting both of those plus more power and 4K gaming support. There was a version of the One S that didn't have an optical drive, but it was a bit of a flop. The Series X is one of the two successors to the One line (along with the Series S), with the Series X having a 4K Blu-ray drive and the Series S not having an optical drive.
Source: I own all of them except for the One X.