Purpose and benefit Precision M121mm inner hex head plug designed to seal threaded ports and sensor openings reliably. Prevents fluid leakage, contamination and pressure loss in hydraulic, pneumatic and fluid systems. Durable construction reduces risk of deformation or failure during installation and service. Key features Material: 304 stainless steel for strong corrosion resistance, wear resistance, strength and long service life. Size: 17 x 17 mm (Dia x H); thread length 11.5 mm (0.45'); thread specification M121mm. Pack contents: 2 hexagon socket (inner hex) plugs. Includes a temperature fluororubber sealing ring for improved sealing under heat and pressure. Accurate threading minimizes crossthreading, loosening or slipping during tightening. Why you need it Provides a secure, reusable seal for unused or temporary ports where leaks would cause downtime or safety issues. Withstands corrosive environments and mechanical wear better than plated or lowergrade metals. Sealing ring and precise threads deliver consistent, leak performance across repeated installs. Practical applications (examples) Automotive and sensor use: seal sensor ports or block off unused openings on engine or transmission components during or storage. Hydraulics and industrial machinery: cap manifold ports on hydraulic pumps, valves or cylinders to prevent fluid loss during system maintenance. Cleaning equipment and piping: close off outlets on pressure cleaners, industrial piping, moulds and hardware fixtures to avoid contamination or spills. Installation tips Use an appropriatesized Allen key for the inner hex drive to avoid rounding the socket. Ensure thread and mating surface are clean before installing the fluororubber seal for sealing performance. Tighten to handtool torque appropriate for stainless steel fittings; avoid excessive force to prevent galling. This M121mm inner hex head pipe fitting plug is a compact, reliable solution for sealing sensor ports, hydraulic fittings and other threaded openings where corrosion resistance and dependable sealing are required.