STOCK IN MARKS BENCH, bottom drawer on the right of the footwell (LABELED).
There are clear button-things that snap into the tops of these tubes to allow for easier labelling, these "things" should be found with the tubes, at each persons desk. I call them niblets, Sarstedt calls them "Colour coded insert, neutral".
Manufacturer's info here.
Tubes P/N: SARSTEDT, 72.692.100
Niblets P/N: SARSTEDT, 65.713