It is hard to review a device that many people take for granted even when they need one. Automotive relays, although complex on their own, are very simple in the grand scheme of things. You provide a power source, a ground, a trigger, and then when triggered, they provide an output.
The EPAuto 30/40A relays do exactly what they are supposed to, they just work. They came well packaged in a foam lined box and include 9in color coded relay harnesses to make connections a breeze, whether you decide to solder or crimp your wires to the harness or use female spade connectors plugged directly to the relay. The relays also feature a metal mounting tab, not a plastic one like many of their competitors.
Overall, I am extremely satisfied with these relays and harnesses. They are built well, easy to use, and do exactly what they are supposed to.
If you are interested in purchasing these relays they can be found here.