Most reels incorporate drag washers made from cork. Cork makes an extremely simple, inexpensive and efficient washer, but it can require more maintenance, especially if used in salt water. Overlubricating a cork washer will destroy it, and cork also can break down under pressure over time. Reels with cork washers should never be stored with the drag engaged. Plastics and composites have begun to slowly replace cork in some reels. Teflon against steel, for example, has an extremely low coefficient of friction, and more important, almost no start-up inertia. However, while noncompressible materials work well, some materials continue to have problems with jerking and high start-up inertia. Many manufacturers tout sealed drags, which can help prevent contamination of porous materials like cork and some carbon fibers, and they can certainly contribute to lower maintenance and increased durability. However, sealed drags do not necessarily imply smoothness. The trick to a smooth drag seems to rest simply in a good design, quality washers and subsequent care.