The one piece FS adapter, essentially a reducing ferrule, is recommended for use in fittings where the ferrule will not be removed. Connections are made and disconnected by loosening the fitting nut and sliding the tube out.

One piece fused silica adapters are available in Valcon polyimide and virgin polyimide for use up to 350°C and in PEEK for lower temperature applications (up to 175°C).

Valcon polyimide is a unique graphite-reinforced composite, specially prepared to maximize mechanical stability at high temperatures. Small blocks are subjected to extreme loads by a process known as hot isostatic pressing, with individual ferrules subsequently machined from these blocks. The result of this two-step process is a fused silica adapter with high temperature stability which far exceeds that of parts produced by conventional molding.