Non-lubricated couplings are used to transmit torque through flexible, stainless steel disc packs instead of gear teeth. It compensates for misalignment by deflection of disc packs instead of gear teeth.
Non-Magnetic Drill Collars are necessary to position a compass out of the magnetic influence of the normal drill string. Non-magnetic drill collars used in the drilling string immediately above the bit have reduced the cost and delay in surveying wells.