The Hiller 83157 O‑RING 2X16 is a rubber sealing ring used to create a tight static seal between two mating parts to prevent fluid or gas leakage in hydraulic, pneumatic, or fuel systems. O‑rings like this are typically sized with an inner diameter and section thickness (here approximately 2 mm thickness x 16 mm diameter), and they are commonly made from elastomeric compounds such as NBR, Viton, or silicone depending on fluid compatibility requirements.

They serve as critical sealing elements in aircraft systems, hydraulic fittings, engine assemblies, and various mechanical joints where leakage prevention and pressure retention are needed.