Reusable nuts with replaceable ferrules in two types:
- Fingertight nuts have a knurled surface designed to allow sufficient sealing force to be applied to the ferrule without wrenches.
- Hex-style nuts allow wrench tightening; however, since they are polymeric, they can break, and are recommended for use only when space is limited and fingers will not fit.
More information on Properties of Polymers and Chemical Resistance of Materials