The MaxGFX V-Tower begins with a 42" long section of 4" diameter PVC drain pipe. Feel free to use your own judgment here, but I personally prefer to cut a 1" slot down one side where the manufacturer's stamp appears. If you want to use a smaller slot, that's your choice. I use 1" because I want a lot of oxygen to be able to get to the roots and media in order to prevent anaerobic bacteria from colonizing, and because the tube squeezes together on its own and shrinks the slot down to about 3/4" anyway. I also do this with a jigsaw rather than a table saw. If you choose to try it with a table saw, you will quickly understand why I choose to take the long way around the block and use a jigsaw in two passes to create the slot.