They’re little individual rubber tubes fitted on each tyne.
Frankly, with a short haired rabbit I have never been sure what it’s for, or how it helps. But I do know that it’s the best comb for getting shedding fur removed. I don’t see why you can’t just use the horse comb as is. The thing to bear in mind is not to pull hard so hair that is about to come out but hasn’t has a chance to loosen free on its own. Don’t pull too hard. Also, the hairbuster comb works best if you comb with it slightly at an angle to the bunny’s back, (not straight into the back like you would if you were stabbing with it) and combing from front to back in the direction of the fur growth. Sammy likes it if I rub her face with one hand and comb with the other. But she doesn’t like it being used on her rump for some reason, which she lets me know by running away, grunting, foot flicking, swearing, giving me the….you get the idea.
Try the horse comb, just gently.