Hardware in the sense of bolts, washers and nuts? I just bought a few hex bolts (M2.5) of various lengths (8/10/12/15mm). Highly recommended to buy some at your local hardware store, especially if you plan to get multiple cartridges. Using a hex screwdriver these are way easier to use IMO; the screwdriver can’t slip out of it, like it can with slotted bolts. With certain cartridges, nuts don’t fit, so you have to use rings instead. But other than ease of use, there’s not much difference; just use what looks nicest to you.