Sovtek 6550WD valve anomaly

[Steve Browning]

As I am moving on my trusty Bass 400, I have no need for the odds bits I have accumulated over the years.

I never felt I had to change power valves but occasionally did so because other people did. I have a sextet of the above that I had changed in my amp but believe them to be fine. I do notice that there are two (slightly) different sizes in the group. I presume they would all be ok together? I was going to flog for not very much but won't do so if there's any issue (although I could sell 2 trios).

Any thoughts, o far more knowledgeable ones?