From me. These are permuations of Reference cables in the Transparent line over the last 15 years or so. I think I am actually wrong on the first one. There are pre MM cables with XL technogy (not MM), and then there are the XL versions of the MM (and MM2) generations of cables. I guess I got confused...
Yeah, it's thoroughly confusing. I find it easiest to rewind to the mid 90s.
At that time there were various levels of Transparent cable with Reference being the top end.
Toward the late '90s transparent developed "XL Technology" and used it to create their new top-end cable called "Reference XL." After that was released they applied the developments of "XL" to the lower lines at which point, in order to differentiate, the levels were referred to as "with XL tech." So you had super, ultra, reference "with XL technology." You can tell an XL version of those cables with an XL stamped to the end of the serial number.
In the early '00s Opus was developed and with it came a new technology called MM and the same thing happened as when XL was developed in that the technology was applied to the lower levels and they were labeled as, "with MM tech." Now they had a Reference XL with MM tech. At the same time they took what they learned with the all-out-assault that was Opus and created Reference MM to slot between Reference XL and Opus. Basically, it's a lot of the features of Opus with a lower price point and simpler construction.
Sometime around 2008 they refined MM technology with some minor tweaks (mostly in housing and connector materials) and called this refinement MM2. All MM (or MM1) cables at the reference level or above could be converted to MM2 at a nominal cost (frankly cheap for Transparent).
So, depending on vintage you have:
Super, Ultra, Reference
Super, Ultra, Reference, Reference XL (with XL tech)
Super, Ultra, Reference, Reference XL, Reference MM, Opus (with MM tech)
Super, Ultra, Reference, Reference XL, Reference MM2, Opus (with MM2 tech)
Some interesting things to note about TA cables....
For the most part the tuning that is done is based on the source impedance although load impedance plays a role as the level goes up. At the Reference level (assuming MM, MM2) it's just a high / low tuning based on typical tube or SS values. With XL and above it's tuned to the specific components in use and the tolerances get tighter the higher you go in the line.
When speaker cables are tuned they take into account component placement (between speakers, left side, right side) along with the placement of the + / - terminals on the speakers and amps. The pigtails on the cables are then arranged appropriately so that they can be connected without having to cross each other at the speaker or amp terminals.