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I believe the copper sealing ring is called hollow bolt ring. It is .06 all the way up to .77 cents.

The braided fuel hose which goes from injector to injector is mercedes part no: 615 476 03 26 (3.2mm Idx1.9)
It is usually sold by the meter. The easiest way to remove it is to cut it off with a razor blade. To install it, you have to be persistent and just keep pushing. I use a blunt instrument to encourage it, making sure not to damage the hose.

Some other part no.s I found for a 1980 300TD regarding fuel hose are:

123-476-30-26 Fuel Hose 14mm id Rubber Exterior $13.10/meter
201-997-08-52 Fuel Hose 9mm id $5.95/Meter
107-476-37-26 Fuel Hose High Pressure 6.00 mm id $26.85
008-997-64-82 Fuel Expansion Hose Cigar Hose 265mm 10 1/2 " length $6.24

What a complete mess. Charles, I hope you have a really great caliper that reads in mm.....good luck