Made of High Quality & Sturdy Material. Copper with nickel-plated. ^^ The wire reducer is great for amp connects, multi-battery terminals, car audio music systems, multiple amplifiers, etc. ^^ The pins work very well for amplifier power connections! It gives you a nice clean install/look. ^^ Amp Input Reducer, 8 Gauge to 16 Gauge, clamp by hexagon screw. It is effortless to use, very effective, and secure connection. ^^ Power/Ground GA adapters, package includes 4 PCS connectors, 4 PCS extra screws, 4 PCS heat shrink tubes, and 1 PCS hexagon tool.