In addition to needing the mulching plug (which, by-the-way is no longer available, so you must buy one on the used market), you will need the mulching kit, which includes 1) a new blade that you install together with the stock blade, 2) 2-new, longer, blade mounting bolts and compression washers, and 3) a new spacer. I bought such a kit last year for an HR215, but when I rec'd it, the instruction sheet said that it also fit the HR215K1 model as well as the HR214 model. This past winter I again bought the same mulching kit for an HR214 that I'm fixing up, but that project is still waiting in line for me to get to it. This mulching kit only showed up on parts diagrams for the HR215K1, but it fits the other models mentioned above.