Thanks for that. The box on the left is not appropriate, as it's BlueRay, and I want M-Disc DVDs. The box on the right is, and I hadn't seen that one yet from Verbatim. Good idea to test before buying, M-Discs are expensive.
I have to say that so far, M-Discs HAVE lived up to the hype, in my experience. I've left them in the cold, the heat, and dropped them on the ground over rocks. No data reading/writingn problems. I just hope they don't disappear as a standard, cause it's not a well-known standard.