Now I don't know much about cork holes and even with a ruler I wasn't sure if this was the right option but it fits perfectly! It was a little easier than I expected, but it doesn't have to be difficult. I'm just glad it fits in my rain barrel because the excess rain washes down the hillside next to my house instead of running into a ditch. The next time there's a storm, I'll stand outside, watch the rain barrel and make sure I've done everything right. added extra super fast shipped.