I would want a steeper angle, but they might keep them out if they can't hook a claw on the inside.

Sides are perfectly smooth, so hoping they won't be able to. I'd like them about six inches longer so that I can angle them down more.

I'll have to talk to the bottle designers at Nestle..

Those will be hard for them to see given their poor eyesight, that's good, but seems to me the entry hole is kinda big, maybe a 2 liter soda bottle cut back so the entry is like 1/2 that size? You can even cut them to leave "Fingers" to be bent over to block re-entry, but allow egress.

Holes are about 1 1/2" in diameter. It was a certain kind of iced tea bottle here that looked like it would do. Nothing seemed to be the perfect size, but I figured 1 1/2" would be ok.

I get what you mean about fingers. Makes good sense. I thought about taping a ziplock bag around the end so that getting in would be impossible but they would just slide out.

I havent found the perfect one yet, but getting closer to figuring out the ideal shape, size and orientation.

What diameter hole do you think would be best for the little brown bats?

If you go to the wildlife control supplies site above and click on the bat excluders , it say's that theirs tapers to 1 1/2 inch

Yeah, that'll work.

We've used 1.5" PVC tubes with good result.s

Cool, thanks. When I got to looking at how commercial ones were made, I saw those pure leaf iced tea bottles and figured they were pretty close. I like how they are square also, so they are easily fastened to surfaces.

Id perhaps want them to be longer, but only so they could be angled lower. I am just getting into exclusion devices, so that was my initial thought anyway.

The price was right lol

Those might work. But they might be a little short.
In that instance, I would have probably stapled a piece of tarp 2 feet wide by 2 feet long to hang over it.
When I cannot Staple I just use duct tape To hold the tarp piece in place.
I use empty caulking tubes, when I must use a tube shaped device But that is rare.

I heard that some times just a screen will work, too, but a tarp I guess is the same. My first stab at excluding. You tape the top and sides, then leave the bottom open if I understand it right?

I do wish it was a bit longer.

Check out the corner flange type. Wicked short, but long enough for bats. Not squirrels.
https://www.wildlifecontrolsupplies.com/animal/PCXXXX.html

Well, had two jobs set up with them. Client heard no more bats after the first night, and the other job it was tough to know as there were only a few using it.

Done, sealed up and paid. Seemed to work.

Excellent!

here's one of my hi tech pcs of old tarp in action
it doesn't matter if its a kitchen vent like in this or an entire gable vent
its the only reason i keep old tarps when they get ripped.

angle down more and you are good to go. if you can'tangle down duct tape some stuff it on the opening. 6 inches is more than enough. I have been using caulk tubes and stuff it for 35 years