Phase testers and speaker spacers are another successful line from MBQ audio. These two soon became a hit when released and continued to have great sales among different countries and regions. A phase tester is considered a must when installing speakers when it could easily find out whether the polarity of a speaker is correct. And speaker spacers are also indispensable for car audio upgrade. Up to 12 models and more of aluminum spacer rings can cover the majority of vehicles and their being waterproof, rust-resistent is ideal for secure and durable speaker installation.