Thanks all, for your input!
One would think water filters would be universal in size or use, but tis not the case.
After looking my collection of filters over today, I found the words "Pro Water Parts" on the top of the water filter needing to be replaced. ClearChoice has a much smaller mouth and is a little shorter. The filter from my former RV does not have a neck.
Thanks specifically to SailerSam and CVL (and google), I think I found the correct replacement: FRE-10-GN .
Assume the problem is resolved unless I add to this chain. Here's hoping the filter arrives before I depart this campground. In the interim, I have been using a filter that attaches to the incoming hose line. I do wish that exact measurements were available in the 'description' section of filters found on line.