Annular BOP Preventer | Hydril, Shaffer & Cameron Guide
The annular preventer (also called bag type, spherical or universal preventer) is the most versatile piece of equipment on the BOP stack since it can close around the casing, drill pipe, drill collars, wireline, and even close an open hole. The rubber packing elements of the annular preventers, which allow this flexibility, are also subject to wear and abuse.
https://www.drillingmanual.com/annular-bop-blowout-preventer-cameron-hydril/