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An extruder would be made of metal or any conductive material that can be heated up to 190 degrees.

The side of the box that the filament comes in will have recommended temperature ranges and you'll want to experiment in increments of plus/minus 5 degrees until you find one that works for your printer/environment. PLA ballparks around 190 and 200-ish whereas ABS will be in the 220-230 degree realm.