I was super nervous to cut into my metal downspout, but measured and eyeballed it a dozen times. Then did it! An hour later we got a big rain and my 60 gallon barrel got filled to the brim and started using the overflow hose. I'm on here buying my second diverter kit cuz a friend gave me another rain barrel for another down spout!

Note: This kit does not come with an overflow hose but I highly recommend installing one. Just get some clear tubing from the toilet section of the hardware store. Then drill a hole in the side of the barrel at the top. A PVC coupler in the hole would be helpful but not necessary if you get the fit right.