Fishbone Gaskets are direct replacements for Kammprofile and Spiralwound gaskets. The procedure generally involves honing, new piston rings, bearings, gaskets and oil seals. Automotive cylinder heads are typically sealed by flat gaskets faced with copper. Silicone is used in microfluidics, seals, gaskets, shrouds, and other applications requiring high biocompatibility. This results in seals, gaskets, diaphragms and other becoming defective quickly. The lower intake gaskets and upper intake manifolds were revised, correcting all these issues. Furthermore, it is extremely corrosive to many materials including seals, gaskets, etc. Engine head gaskets and camshafts are sold as well. Some carburetor float bowl gaskets are made of cork, for example. The quality of rubber seals, gaskets and paint was particularly poor in the early 1990s. They are used in conjunction with ring type seal gaskets. The heads are sealed to the block by copper gaskets and stainless steel o-rings. More asbestos will be dropped, which will exacerbate the problems of cylinder head gaskets. Knife edges pressed into copper gaskets are used for high vacuum. Stone fibers are used in gaskets and friction materials.