The Tri Clamp to NPT cone adapter has a significant advantage over its flat-faced counter part by using a tapered face to guide liquids down towards the NPT fitting, reducing turbulence, drag, and most importantly to prevent any kind of pooling.
NPT is a standardized fitting that is commonly used for joining pipe. Due to the tapered threads (wider diameter at the base of the threads, similar to a trapezoid) the male fitting will tighten the further it is threaded into the female. NPT follows the technical standards provided by the American National Standard Pipe Thread standards, often called national pipe thread, which is where the confusions with NPT arises, as NPT is specifically an acronym that refers to tapered pipe.
Sizing NPT/NPS is based on the nominal pipe diameter, and not the outside diameter (OD) of the threads. For example: A 1/2" NPT male has an outside thread diameter of approximately 3/4", but as stated the correct NPT size is 1/2", including the counterpart female. Notice: While NPT and NPS threads may be joined together, their threads may not create a proper seal, be loose fitting, or not form an optimal connection.