A hollow hex plug with SAE‑MS straight threads is a precision-engineered fitting designed to seal or close the end of a female SAE‑MS threaded port or component while allowing internal access through its hollow center. The fitting features a male straight thread (SAE‑MS) and a hexagonal head for easy tightening or removal with a wrench. The hollow design enables functions such as pressure testing, venting, or temporary instrumentation connections without disassembling the system.
These plugs are widely used in hydraulic, pneumatic, instrumentation, and fluid systems across industries like aerospace, oil and gas, chemical processing, and industrial manufacturing. When installed with an O-ring or bonded washer, the straight threads provide a secure, leak-resistant seal suitable for high-pressure and demanding operational conditions.

