Review on 🚗 Upgrade Your Vehicle's Electrical System with Gebildet JD1912 Car Relay Harness – 12V 40A 4 Pin SPST Harness Sockets for Automotive Truck Van Motorcycle Boat (Pack of 2) by Brandon Wynen

Not bad for the price, but no reason to be happy. They are rated for 40 amps but I don't know if I would run that many through them, maybe 30 amps at most for the safety margin. The main power cables aren't that heavy, but if you connect them to a 30A circuit along the cables they should be able to handle the current, but a 10ga cable is recommended for the rest of the circuit. There are no interference suppression diodes on the coil side of the relay. I added my own to curb power surges caused by the relay coil when de-energized to protect my computer module in the car. They're not really weatherproof, so I wouldn't install them where they might rain or be splashed with water. I used them in my car under the dashboard so they are not exposed to outside conditions. I'm not criticizing these relays for being good, but if you're going to be using them in harsh environments I'd say spend a little more money and do something to expose them to splash or fog.