Technically, it's not a "UCL" because the substrate isn't water-white glass - BUT... The AR coating on these is so incredible, it performs just as well, with transmittance levels at a steady 99% Once you get one in your hands and look at the beautiful deep purple reflection of the AR, you'll be glad you ordered.
Light transmission: 99%
Substrate: Float glass
Coatings: Multi-layer broadband AR - 2-sides
Thermal durability: Good - typical of most glass