No rule for this one
No ending or word group predicts the article of Headset. Learn it as a pair and say it out loud: das Headset.
das Headset
It's das Headset. Headset is neuter, plural die Headsets.
Ich brauche ein Headset.
I need a headset.
No ending or word group predicts the article of Headset. Learn it as a pair and say it out loud: das Headset.