B&K 3/8"x20' Copper Refrigerator Tube. It is used for refrigeration applications. 99% pure copper, annealed for ready bending, with outer diameter measurements applying to refrigerator tubing. Mueller Industries dehydrated refrigeration coils are made to ASTM standard B-280. The copper tube is cleaned, nitrogen urged, capped (with standard yellow caps) and shrink-wrapped to an air tight seal.