This is what's printed with .6mm Harden still nozzle If you are printing PLA ABS PETG TPU and all other types of filaments. If you're constantly changing between different types of filaments and different temperature types, the harden steel is your best way to go. But if you're only printing just PLA, you can use just a brass nozzle which is a great heat. Conductor. Easier to warm up faster, but the harden steel will last longer. Less clogging and always keep. It's fine tip and Prince amazingly no matter if you have a 0.6 mm or a 0.4 mm nozzles in the harden steel. So if you're using different filaments all the time then yes I do recommend using a hardened steel nozzle

It’s a nozzle well