This is a RAM ball that the Insta360 "GPS Preview Remote" rubber mount can be put on if you don't have room on your bars.
v2 is a plain design with no embossement on the end.
v4 is 1mm larger in diameter than v2 so the remote mount fits a little tighter. It also has a dog paw embossed on the end. In the photos v4 is the one with the fuzzy skin. No, that surface finish is not the result of storing the filament underwater, it's intentional to see if it offered more "grip". I think it does but I may be imagining that.
I have used a version of v2 with fuzzy skin and it worked fine, but v4 should work a little better. Your mileage may vary. If you don't mind dog paws I'd go with v4. If you DO mind dog paws or want to get a LONG bolt to go all the way through the mount, use v2.
Insta360_Bigger_Remote_Mount_v4.stl | 1.3MB | |
Insta360_Remote_Mount_v2.stl | 1.2MB |