Ateco230 2 7/8" Bismark Metal Piping Tip - Great for filling donuts, cupcakes, elclairs, and other pastries

Q: How wide is the opening where the filling comes out?

Best I can measure it appears to be about 5 mm in diameter or about 1/4 inch.

Q: Has anyone used this to fill churros?

No, I haven't. There's a learning curve to make sure that the tip is level when inserted or else the filling will come out the sides. Yeah, of course I've done that...more than a time or two! Unlike something larger like a donut, I would think that there's not much room for error when trying to fill a thin churro. However, it does sound yummy so give it a try. What's the worse that can happen? You eat the boo-boos????

Q: Could this be used to fill a Kong dog toy with peanut butter? I'm looking for an alternative to the disposable spray cans and tubes.

Smash up a dog biscuit, rub peanut butter into it, put into Kong with butter knife, smooshed onto insides of Kong. I never buy Kong premade stuff. Dog will love it