They are great and fit perfect.

The Aluminium Fan shroud fits the Mk3S extruder but does not have the second bracket for the Mk3S+
the shroud has an integrated mounting screw thread, so you don't need to fiddle with thin square nuts during installation
performance is certainly better than my previously melted fan shroud.

I suspect that blobs of doom, will be easier to clear off the aluminium shroud, than the previous plastic shroud, however I hope there will be fewer blobs of doom, because the aluminium fan shroud is unlikely to droop and catch on models on the build plate, in the first place.