An exceedingly reasonable question, @axl. @fivestrideline nailed it (and may in the process have added a new quote to my arsenal.)
This is also a great question! It’s the Equifit SilentFit shown here in Parachute Size (aka O/S.) And yes, her ears Really Are that big:
I personally went for versatility: I got the earless Fenwick mask (in XL, in case anyone’s wondering about sizing reference; a L probably also could have worked but I like the looser fit best), the aforementioned SilentFit bonnet, and a pair of the Equifit contoured ear plugs.
Two out of three of these things worked.
With one emphatic shake of her head, one ear plug sailed straight into her water bucket and the other somehow popped OVER the 8’ stall wall into her neighbor’s territory. Still don’t know how she managed that but it was enough to terminate the Great Ear Plug Experiment.
To actually answer your question, though: The difference between no bonnet/no mask and bonnet + mask is amazing. She was previously on 11 150 mg traz 2x/day plus I was acing her for every ride and she was still blowing through the ace almost every day despite the fact that I’d come out very early or very late when things were quiet. She’s now on 5 150 mg traz 2x/day, I only ace her when something’s going on (maybe a day every couple weeks), and yet the pendulum has still swung back to Boredom vs. Terror. (These are the two emotions when dealing with a stall-rest horse.)
But I haven’t done science on Mask No Bonnet vs. Bonnet No Mask vs. Bonnet Mask, and while I am usually very pro-science, in this specific instance I have surprisingly little desire to do so. (Since there is no real scientific evidence for why or how the mask would work, that also hurt me in my soul. But broadly, I would rather that my soul hurt vs., say, some of my bones.)
That said, they put one on her during her previous rehab stint (the one where I paid people, instead of DIYing it) while she was on the water treadmill and she seemed very chill about it, and a few people at my barn have them and seem to think they help. So… can’t hurt anything except your wallet, I guess?