These are stainless steel swivel nuts. Most Swivel Nuts on the market will be Nickel-plated brass, which is an acceptable material as your beer never touches it. The downside to these Nickel plated products is the potential for rust. Using our Stainless Steel Swivel Nut, you will not need to worry about rust again! Buy products that will last a lifetime, buy stainless! This is a 303 Stainless Steel 1/4" Flare Swivel Nut. Great for use with our KEG602 & KEG604.