The 3M™ Scotchlok™ 2000T CU Series Connectors are copper inline sleeves that are for use with copper conductor cables of the same size when connecting copper cable to copper cable only. When you need a product that connects copper and aluminum cables use the 3M™ Scotchlok™ 2000T CU/AL Series Connectors. These connectors feature aluminum inline sleeves that are used with aluminum or copper conductor cables of the same size. For connecting cables of different sizes and types, the 3M™ Scotchlok™ 2000T Reducer Series Connectors are your answer. They are aluminum inline sleeves that are applicable for both aluminum and copper conductors, and because the barrel diameters at the connector ends are different, they allow connecting conductors of different size.