I got a replacement heater core and this one came with the duct holes. That'll make it easier. A simple disassembly of the core's shell, drop the duct work in, and we're good. Then put on the brackets, the valve to stop the flow of hot water (thank you, thank you, thank you Rotax and Sling for making it so I don't need to suck air off an exhaust manifold that may be rusted throw in 10-20 years and tossing carbon monoxide (CO) into my face!), and off we go. Some things to note. The tubes are the same length. They come that way. One tube just goes on, no biggie. The other tube needs to not only be cut, but to have a piece of hose the length of the valve cut out, too. Just RTFM and do EXACTLY like it says in the instructions. Here's what happens if you don't read the instructions: 1) Install the first hose. 2) Install the top (closest to the core) of the second hose, cut it for the top of the valve. 3) Put the entire bottom of the hose on the bottom of the valve. 4) See that it is completely wrong because the second hose is too long, and assume that the wrong hose was used because the two weren't actually checked to start with. 5) Quickly remove the hoses, mount the complete hose up against the valve, cut it, too (assuming it was the shorter hose). 6) Put the two hoses next to each other, see that the one on the valve is somehow too long now. 7) Realize that the builder is an idiot and should have read the instructions. 8) Read the instructions, cut out the correct amount of hose. 9) Get a SharkBite brand (because that's what the hardware store had) brass 3/4" x 3/4" straight coupler and use some Zebra pipe clamps to join the extra cut hose. 10) Write out what can go wrong when not reading the instructions, and realize that most likely no one else will read it. In fact, if you read this, send me an e-mail at edwardhefter@gmail.com and let me k ow where you saw this and I'll Venmo you $10! Aside from all that, it was pretty simple!