Phase tester is sturdy and durable, maximizing durability, assurance, This phase meter can be used to failure test and troubleshooting. This is a very , practical phase meter, which will bring you a good experience. Features -Color: Black. -Material: ABS, electronics. -Size: About 11.00X7.00X2.50cm/4.32X2.75X0.98in. - Perfect for safely troubleshooting and testing audio systems, portable to use - This phase meter can speakers of all car, such as small treble, door speakers, subwoofer, etc. - Press the 'test' button on meter, 3 flash red light indicates that the speaker output is in positive phase (correct connection) ;. - 3 red light flash indicates that the speaker output is in negative phase (reversed connection). - The product is practical and reliable, with good stability and durability, and will be your . How to use: Play or 2, can check the left/right is right or not. Play section 3 or 4, the sound speaker will produce a fixed frequency signal. Package list: 1 x Speaker Test Phase Meter 1 x CD