A trim assembly (14; 114; 214; 314; 414; 514) adapted to be installed within a fluid flow control device (10; 100; 200; 300; 400; 500) comprising a valve body (12; 112; 212; 312; 412; 512) and a control element (18; 118; 218; 418; 518), the valve body (12; 112; 212; 312; 412; 512) defining an inlet (20; 22; 24; 120; 122; 124; 220; 222; 224; 420; 422; 424; 520; 522; 524), an outlet (20; 22; 24; 120; 122; 124; 220; 222; 224; 420; 422; 424; 520; 522; 524), and a throat (26; 126; 226; 426; 526) disposed between the inlet (20; 22; 24; 120; 122; 124; 220; 222; 224; 420; 422; 424; 520; 522; 524) and the outlet (20; 22; 24; 120; 122; 124; 220; 222; 224; 420; 422; 424; 520; 522; 524), the control element (18; 118; 218; 418; 518) disposed within the throat (26; 126; 226; 426; 526) and adapted to be displaced between a first position and a second position for controlling the flow of fluid through the valve body (12; 112; 212; 312; 412; 512), the trim assembly (14; 114; 214; 314; 414; 514) comprising: a valve seat (42; 142; 242; 442; 542); a retention ring (44; 144; 244; 444; 544); and a seal compressed between the retention ring (44; 144; 244; 444; 544) and the upper ring portion (48; 148; 248; 448; 548) of the valve seat (42; 142; 242; 442; 542) to provide a fluid tight seal between the trim assembly (14; 114; 214; 314; 414; 514) and the valve body (12; 112; 212; 312; 412; 512), characterized in that: the valve seat (42; 142; 242; 442; 542) is adapted to be threadably connected to the valve body (12; 112; 212; 312; 412; 512) adjacent to the throat (26; 126; 226; 426; 526), the valve seat (42; 142; 242; 442; 542) comprising a seat ring portion (46; 146; 246; 446; 546) and an upper ring portion (48; 148; 248; 448; 548), the seat ring portion (46; 146; 246; 446; 546) defining a first seating surface (36; 236; 454) adapted to be engaged by the control element (18; 118; 218; 418; 518) when the control element (18; 118; 218; 418; 518) is in the first position, the upper ring portion (48; 148; 248; 448; 548) defining an outer cylindrical surface (58; 158; 458; 558) and an inner cylindrical surface and adapted to be disposed opposite the throat (26; 126; 226; 426; 526) from the seat ring portion (46; 146; 246; 446; 546); the retention ring (44; 144; 244; 444; 544) is threadably connected to the upper ring portion (48; 148; 248; 448; 548) of the valve seat (42; 142; 242; 442; 542) and defining an outer cylindrical surface (76; 176; 476); and the seal (84; 184; 284; 484; 584) comprises a graphite material. a valve seat (42; 142; 242; 442; 542); a retention ring (44; 144; 244; 444; 544); and a seal compressed between the retention ring (44; 144; 244; 444; 544) and the upper ring portion (48; 148; 248; 448; 548) of the valve seat (42; 142; 242; 442; 542) to provide a fluid tight seal between the trim assembly (14; 114; 214; 314; 414; 514) and the valve body (12; 112; 212; 312; 412; 512), characterized in that: the valve seat (42; 142; 242; 442; 542) is adapted to be threadably connected to the valve body (12; 112; 212; 312; 412; 512) adjacent to the throat (26; 126; 226; 426; 526), the valve seat (42; 142; 242; 442; 542) comprising a seat ring portion (46; 146; 246; 446; 546) and an upper ring portion (48; 148; 248; 448; 548), the seat ring portion (46; 146; 246; 446; 546) defining a first seating surface (36; 236; 454) adapted to be engaged by the control element (18; 118; 218; 418; 518) when the control element (18; 118; 218; 418; 518) is in the first position, the upper ring portion (48; 148; 248; 448; 548) defining an outer cylindrical surface (58; 158; 458; 558) and an inner cylindrical surface and adapted to be disposed opposite the throat (26; 126; 226; 426; 526) from the seat ring portion (46; 146; 246; 446; 546); the retention ring (44; 144; 244; 444; 544) is threadably connected to the upper ring portion (48; 148; 248; 448; 548) of the valve seat (42; 142; 242; 442; 542) and defining an outer cylindrical surface (76; 176; 476); and the seal (84; 184; 284; 484; 584) comprises a graphite material. the valve seat (42; 142; 242; 442; 542) is adapted to be threadably connected to the valve body (12; 112; 212; 312; 412; 512) adjacent to the throat (26; 126; 226; 426; 526), the valve seat (42; 142; 242; 442; 542) comprising a seat ring portion (46; 146; 246; 446; 546) and an upper ring portion (48; 148; 248; 448; 548), the seat ring portion (46; 146; 246; 446; 546) defining a first seating surface (36; 236; 454) adapted to be engaged by the control element (18; 118; 218; 418; 518) when the control element (18; 118; 218; 418; 518) is in the first position, the upper ring portion (48; 148; 248; 448; 548) defining an outer cylindrical surface (58; 158; 458; 558) and an inner cylindrical surface and adapted to be disposed opposite the throat (26; 126; 226; 426; 526) from the seat ring portion (46; 146; 246; 446; 546); the retention ring (44; 144; 244; 444; 544) is threadably connected to the upper ring portion (48; 148; 248; 448; 548) of the valve seat (42; 142; 242; 442; 542) and defining an outer cylindrical surface (76; 176; 476); and the seal (84; 184; 284; 484; 584) comprises a graphite material.