Used (for parts) A/C compressor line.  This is just the segment that bolts to the compressor, as the rubber hose ends have been cut off.  This would be used for a GM 3.8L-V6 swap, you can cut off the hose clamps and fabricate your own hose with this segment.  This is off of 00-02 3.8L-V6 Camaro/Firebird compressors.