Just sounds like Blu-ray Discs and the seller is using confusing terminology. Nothing fancy about the discs or codecs as they're BD compliant. Think it's more to ensure people don't buy them thinking that they are DVDs.

Merlin is 65 hours of content. Assuming no overhead which is obviously wrong, but still, it works out as around 13mbps for video and a 640k audio track. Which is not amazing, but certainly serviceable for 1080p H.264 content.

Hmm.... then I really wonder why on earth the regular region B BBC editions, say single season 4, consists of a whopping 5 (five) discs all on its lonesome.... ? 😅
https://i.ebayimg.com/images/g/XRgAAOSwmIJe0WZt/s-l1600.jpg

(granted, there are the 'extras', but still... ?)

"ultra-clear" is play on marketing scam.

All blu-ray burnables discs have varying of quality, just go by reputation on a trusted forums.

Cheers,

Original discs aren't region free
They could be MPEG 4 AVC, they could be H.265.
Typically 1920x1080 MPEG 4 is 9GB per episode on a blu-ray.
I don't have any 4k blu-ray discs but a downloaded episode is usually around 3-6GB and those are usually h.265 and I doubt the original source of those was h.265......but I don't remember there ever being a 4k release of Merlin (I still have my DVD of all five seasons)

https://www.amazon.com/Adventures-Merlin-Comp … y/dp/B092QPB72H
15 discs for original blu-ray

So likely a 1080p release with extras removed or re-compressed, may or may not be higher capacity discs. Possibly compressed with h.265 since I don't see why someone would re-compress MPEG 4 into a lower bitrate MPEG4 since h.265 is the craze nowadays.

8k? Sounds like ultra def to me.

Region free perhaps means that the BD has A/B/C region lock (all of them)..
So it can be played in all regions. This practice isn't unusual for BDs these days. Region lock no longer is as relevant as it was in the DVD days.
Maybe the industry had learned from those beloved region-free DVD players everyone bought (RC-0; with RPC-1 drives).
Or the tutorials that told users how to get into their players' service mode.

If it plays on a Blu-ray player... it's a Blu-ray. Just a Blu-ray. Well it could be a DVD too I suppose. Due to the standardization of the format the specifications are pretty locked down, you can't do something new or compatibility would be a nightmare.

Not sure why eBay bootleggers would call them ultra-clear.

That said eBay bootleggers are also the kind of people that would release something with crap compatibility, so it is possible it is different, but... why care?

^Commercial Video CDs w/ MPEG1 can still be played on BD players, too. I tried.
Unfortunately, DVD or BD players don't support the chapter selection feature of VCDs.
A Philips CD-i player, 3DO, CDTV/CD32 or compatible PC/Mac player software was required for this.

Edit: Super VCDs may also work, I suppose.
They're quite similar to DVD Video, both use MPEG2.