Mill Finish is the natural appearance of the aluminum as it comes from the rolling mill (Alcoa, Reynolds, Kaiser, or Alcan) or the extrusion mill. It is as is with no external mechanical or chemical finishing. Extruded metal is considered mill finish. All aluminum has an oxide of some varying thickness. Anodizing is a very heavy controlled oxide.
As they are so small of approximately 5-20 micro-metres in diameter, they do not need valves, as there is a distinct flow from the arterioles supplying the capillary with blood, and the venules draining the capillary within the double circulation.
There are networks of capillaries in most of the organs and tissues of the body. These capillaries are supplied with blood by arterioles and drained by venules. Capillary walls are only one cell thick (see diagram), which permits exchanges of material between the contents of the capillary and the surrounding tissue.he following diagram summarises the sequence of blood flow through the heart, arteries, arterioles, capillaries, venules, veins, then back to the heart: The following diagram summarises the structural differences between different types of blood vessels. More information about this also follows in the next section.