Abstract: A fitting assembly for forming a fluid-tight seal with an end of a stainless steel tube is provided with a seal seat that is composed of a material that is harder than the material that the stainless steel tube is composed of. The stainless steel tube may be gripped between a bushing and the seal seat to form a fluid-tight seal with the stainless steel tube. The fitting assembly may be tightened so that the stainless steel tube is deformed between the bushing and the seal seat of the fitting assembly.

Abstract: A fitting assembly for forming a fluid-tight seal with an end of a stainless steel tube is provided with an adapter that is made of a material that is different from the material that the seal seat is made of. The material selected for the adapter is relatively less expensive than brass and the manufacturing method for making the adapter is relatively less expensive than that for making conventional adapters that are entirely made out of brass. According to an embodiment of the present invention, the adapter may be made of iron. According to an embodiment of the present invention, the seal seat may be made of a material that is softer than the material that the stainless steel tube is made of. According to another embodiment of the present invention, the seal seat may be made of a material that is harder than the material that the stainless steel tube is made of.