What is it for and what do I need to do w/ it. My friend has a HBL BP 150.1 and this is on there between the Batt and Gound jacks. I'm helpin him hook it up but we don't kno what to use this for and he doesn't have his manual.
Also, on a side note which amp would you take? Kicker KX 400.1 or MTX Thunder 421D