XTS antenna, or an MTS antenna. I used to have a Motorola Type 2 system here at work with about 350 radios on it. Most were Motorola MTS2000s, some where XTS2500 and we had some EFJ 5100's. The antennas were all interchageable.
I don't know about the XPR antennas, other than a brief trial with did with MotoTrbo, I haven't had much experience with them. I think some of those had a GPS antenna function in them, so not 100% sure the antennas are fully compatible. I'm sure someone here knows.