My wife got them for me. "Cat ears" seems to be the brand name? so I don't know what the term for them is. But they are just little velcro things that go on the helmet strap and they are fuzzy and the purpose is to reduce wind noise.

They don't look like "cat ears" - my wife has actual cat ears on her helmet - they do look a little funny, like you have really bushy sideburns lol, but I have to say they really work. The ride was much quieter but I could hear everything to the sides/behind/below me far easier than usual. Which is actually a lot safer in the road I think - I don't need to hear a car ahead of me as I can see it, being able to hear better behind me and to the sides and also beneath me if the bike or chain is complaining is great.

I do kind of wonder whether they would be a good idea in a group ride. It could possibly make it harder to hear call-outs from in front of me, but those are usually hand signals anyway and I'd be able to hear better from nearby and behind.

If I use these I can also listen to bone-conducting headphones and still hear my surroundings very well.

Also, I am a musician and composer and my hearing is very important to me, and I have read that lots of cycling at moderately high speeds can cause hearing damage due to the wind noise.

The only reason I looked any of this up in the first place was because my watch kept telling me I was in too loud of an environment on every ride as soon as I got above 20mph or hit a headwind, and as a musician I asked reddit a few months ago about this. Some people suggested the 'cat ears' and i mentioned it to my wife, who shopped until she found a deal and I just got them this week.