Help to determine a spare part of AD-5590A-01

[qanda]This thread is about the Sony NEC Optiarc 20x DVD Multi Writer Black. Click here to see full specs[/qanda]I disassembled my drive to set up mode slave. When I tried to assemble it back I found a piece of PVC pipe, blue color, diametr 8 mm, heigt 5 mm (see a photo of a longer pipe of white color: http://www.chip-dip.ru/product0/photo71517507.aspx). Is it a part of this drive and if yes,
where should it be installed? Can anybody have a look at his or her drive? I didn`t find service manual for AD-5590. Thank you very much.