The thread fittings

Threaded fittings on their internal (female) or outer (male) surfaces have screw threads (built-in grooves) intended to accept connections with corresponding threads. Threads are called straight threads that provide an easy connection but no guaranteed seal. Tapered threads are designed to give a tight seal required for pneumatic applications. These precise threads generate a "dry fit," which means they seal without the need for additional sealant, which is essential in an application where added sealant may result in contamination or corrosion.