What does MV on a hitch stand for?

[TubeTruck]

Just browsing my options once I get my Suburban set up for towing. I was looking at weight distribution hitches and I can't figure out what the MV stands for.

https://www.amazon.com/17063-Round-...Curt+17063&qid=1569677699&s=automotive&sr=1-1

https://www.amazon.com/17222-Round-...Curt+17063&qid=1569677699&s=automotive&sr=1-3

 

[Craig 85]

I looked at the Curt site. I think MV is the model for a round bar system. The square tube style is referred to as a Trunnion .