Popular male brass threaded hex nipple reducer:

Materials: Connection, valve, valve body and unlocking sleeve: Brass , spring, circlip and locking balls, Stainless steel, seals, Viton (PTFE coated)  

Operating range: For liquid media with temperatures up to +160°C, e.g. for cooling circuits on plastic machines (+200°C on request) 
Optional: with unlocking protection (standard by stainless steel couplings) -S 
To differentiate the brass couplings easier: 
Coupling socket: Sliding sleeve made of plain brass = shut-off, sliding sleeve made of nickel-plated steel = valveless 
Coupling plug: Hollow hex plug for closing and terminating pipes. Internal head shape is hollow and hexagonal for increased leverage with a wrench during installation and disassembly. Male National Pipe Taper (NPT) threads for creating a tighter seal than straight threads.