This is a thermal protection device for Hybrid Audio Technologies tweeters. It is required when running any tweeter actively without the protection of the factory crossover on the Imagine, Clarus speakers or Legatia speakers. It is designed to protect the speakers from damage caused by turn on pops, misadjusted crossover frequencies or auto calibrating processors that deliver a signal beyond the frequency range of the tweeter. If you use the Imagine or Clarus speakers with their included crossovers these are not necessary.   These are required for approval to any warranty claim where a tweeter was damaged becasue of the above mentioned causes.   Includes: One pair (2 pcs) of tweeter protectors