When a seat pan fits poorly it can make good backrests and ergonomic desks ineffective. In addition to raising and tilting seats for correct posture, some seat pan inserts also adjust sitting pressures under the buttocks and tailbone. Special contour and cutaway sections can help people with hemorrhoids or with an enlarged prostate, with injury to the tailbone or anal areas, and after pregnancy.
There are two occasional drawbacks: they may compromise head room in your car, and they may make built-in low back support hit you in the wrong place.