Wireline core barrels, inner tube and inner tube assembly in particular constitute the most important part of these sets. Both ends of the inner tubes are made of male threaded cold-drawn steel tubes. The types of threads at both ends are the same. Since the part where the core is inserted will be eroded faster than the top section, use of the tube by turning upside down from time to time will extend its service life.
The core lifter case where the core lifter (see 8 ) is inserted is located at the bottom side of the inner tube. There is a case inside the core lifter and just above the part where the core lifter is inserted and the core lifter can be placed there (see 10) . This ring prevents the core lifter to be dragged into the inner tube together with the core.
The inner tube assembly is located at the top of the inner tube.