A stem packing assembly including a first annular member defining a central axis, a second annular member defining a central axis coaxial with the central axis of the first annular member, and an annular energizing member defining a central axis coaxial with the central axis of the first annular member. In an embodiment, the stem packing assembly can have a leakage rate according to ISO 15848-1 of less than 1×10−4 mgs−1m−1 for at least 500 cycles at 160° C., and less than 1×10−4 mgs−1m−1 for at least 500 cycles at −46° C. In another embodiment, the first annular member can include a PAEK, the second annular member can include a PTFE, and the annular energizing member at least partially includes a PTFE.