RVCarpenter - Welcome aboard iRV2
I'm sure someone has some information on one of the specific vent toppers that you posted and they'll post that up rather quickly.
As another alternative though, I went with a powered vent on my black tank as I used to occasionaly get odor out of the toilet when it was flushed and one of the fantastic fans was running inside the coach. It turned out that the fantastic fan tended to create a small amount of negative pressure inside the coach, and when the toilet was flushed the fumes were pulled in from the tank.
I was concerned that the static type vent wouldn't move enough air when it there was not wind blowing over the vent so I went with the
Lil Stanker tank vent. Since it is powered, it is constantly moving air. Since the fan iside the vent cover is a very small muffin fan (typical of what you'd have inside your computer power supply) it is very quiet and draws very little power. Since it only consumes millieamps, you can actually leave it on all the time.
Another member did a review with pictueres in the product evaluation section yo might find interesting.
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Joe & Shelly, Justin, Tyler, Alyssa | Butler PA
2008 Tiffin Allegro Bus 43QRP|Cummins 425|Honda CRV