This kit includes both the outer cover (which can be removed from the helmet easily without any tools) and the inner assembly that mounts to the helmet shell via three phillips-head screws. I would think 99% of the time only the outer cover would need replacing as this is what operates the vents, but if for some reason you need to remove the inner assembly the two outside screws are covered by styrafoam on the inside of the helmet, and will be quite difficult to access. Luckily I did not have to replace that component.
Overall this is just what I needed, as the vent switch tab on my helmet broke off and the only way I could operate it was sticking a screwdriver into it.......not the most convenient method when out riding. This part made it just like new in about 30 seconds time.