M&K Tripole K4 or Surround 55 MKII?

My first post here.
Does anyone know the difference between these 2 M&K surround tripole speakers?

'K4' and 'Surround 55 MKII'

They're both advertized as tripoles and look similar. I don't know if one model is newer and/or higher spec than the other. I've tried researching on the web but can't find much info anywhere.

I do not recommend the M&K K4 (tripole) speakers.
They are too small, IMHO.
(And Yeah, I have them, unfortunately, as my rear speakers.)
In a small room, they "might" work.
However, in my rather large room, (16' x 24') they just don't fill the room enough.
(Which is kinda funny, as the matching LCR speaker, the K7 fills it nicely, and I wish I had bought two more K7's instead of the K4s.)

My two cents worth.