Annular Preventers (Figure 1.9) are rubber donut shaped seals that close around the pipe sealing the well. They can also seal the well with an absence of pipe in the hole. Stripping occurs if an annular is closed around the pipe, and the pipe is moved upward or downward during this time. Witness accounts stated that stripping had occurred on the Deepwater Horizon and pieces of rubber were observed. The stripping could have weakened the annular preventers.