Uxcell Outer Hex Head Plug 304 Stainless Steel Solid Thread Corrosion Resistant Bung Plug Pipe Fitting 2Pcs 1.02" x 0.98"(L x Max.D)

304 Stainless Steel for corrosion resistance, ductility at high temperatures, and low magnetic permeability.

It is a silver tone outer Hex Head Pipe Connector that is for closing and terminating the end of a pipe.
Great for blocking off intake manifold water ports, water pump ports, water temp and oil sender holes, engine block .
In order to enhance the sealing performance,you can use O rubber ring.