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A type of lost-circulation material that is thin and flat in shape, with a large surface area. Flake LCM can be prepared in various sizes. It should be insoluble and inert to the mud system in which it is used. Its purpose is to seal off fluid loss zones in a well and help stop lost circulation. Mica flakes and pieces of plastic (cellophane) sheeting are commonly used. Often, granular, flake and fiber LCMs will be mixed into one LCM pill and pumped into the zone where losses are occurring.