Buyers Products Electric Trailer Brake Controllers provide reliable control for trailers with up to 4 axles equipped with electric brakes.5422003: A time-based controller applies braking power at a fixed rate, not proportional to the amount of pressure applied to the brake pedal. It's a reliable, cost-effective approach that makes it great for towing small and medium trailers with up to 2 axles (4 electric brakes) for items like ATVs, riding lawn mowers, or building materials5422004: Proportional braking corresponds to the amount of pressure your foot is putting on the brake pedal in your cab. The trailer's brakes will match any situation, from a gradual slowdown to a sudden stop. This feature results in smoother performance and reduced wear on the brakes making it ideal for heavier trailers with up to 4 axles (8 electric brakes) like items like dump trailers, construction equipment, or excavating machineryThe brake controller conveniently mounts inside the vehicle, and quickly connects to the vehicle's trailer wiring. An easy-to-adjust trim wheel lets you set the power level needed to brake and a slide switch lets you engage the trailer brakes brake whenever needed. Mounting bracket and hardware are included. Material: Metal.