This is a mod for the SeeMeCNC ezstruder, allowing it to use a MK8 hobbed gear and bowden passthrough connector. You'll need an ezstruder, as it uses the bearing arm that comes with it. Technically you could source the bearing and spring yourself, but it helps to start with the original. You'll also need an E3D (or Prometheus) passthrough connector for the bowden tube, and a MK8 hobbed gear.
The end result is the MK8 provides ~34% more torque than the original MK7 gear, and the passthrough means that the bowden tube runs right up to the gear, helping keep the filament snag free.
EDIT After lots of testing, here are the existing issues: The faceplate which helps keep the red arm aligned can loosen over time, I need to embed a nut for to hold the screw instead of just threading into plastic. Also, the spring pressure is a liiittle strong, with one spool of ABS the filament would sometimes get flattened.
I didn't mark down which screws need replacing, but you'll find that some of the original screws for the ezstruder will now be a touch too short.
The cylinder that replaces the aluminum one in the original has BSP threads for the passthrough connector, so it may be helpful to print it on a resin printer if you have access to one, but it'll probably still work on a regular FDM printer.
All of the parts are 1-1 replacements, so just print them out and assemble exactly as they were in the original. Also, you'll notice that the passthrough connector will prevent the bowden tube from going down, but to stop it from creeping up into the hobbed gear, wrap some kapton (or other strong tape) around the tube as shown in the picture to keep it locked solidly in place.
All of the parts should be printed with very high infill, preferably out of PLA as it's stiffer than ABS. The faceplate helps keep the bearing arm aligned, so that should be printed solid.