Feature: 1. Automotive Audio System: The phase polarity tester is ideal for safety testing and troubleshooting car audio systems for everyday use. 2. Function: Polarity tester can detect the correctness of the positive and negative connections of speakers, such as door speakers, subwoofers, small tweeters, etc. 3. Battery Indicator: The phase meter low battery indicator illuminates to indicate a low battery and is useful for testing speaker polarity. 4. Long Durability: ABS shockproof housing, sturdy and durable, ensures a long life of your phase tester and reduces maintenance costs. 5. Compact Design: Unique fashion design, compact and lightweight, easy to use, professional manufacturing, high reliability. Specification: Item Type: Speaker Polarity Tester Material: ABS Battery Type: 1 9V 6F22 dry battery (not included) Uses: It can be used as a tuning assistant, mainly used to detect whether the positive and negative poles of the speaker are connected correctly.. Package List: 1 x Speaker Polarity Tester1 x Test CD