I used ABS for all the parts, and you will need 1 of each STL part except for the following:-
Counter Front/Back - 2
Counter reel 2 - 2
Lost motion - 2
Lost motion -Drive Pin - 2
You will need some extra components to complete the build:-
1 piece Ø 2 mm steel rod 80 mm long
2 piece Ø 2 mm steel rod 100 mm long
2 Springs as used in a retractable pen
You may also need a:-
Ø2 mm drill for the 3 holes in the Mainframe for securing then ends of the Ø2mm shafts.
A Ø2.1 mm drill for drilling out the bores in the parts that are a running fit on those shafts.
Acetone to solvent bond some of the parts together.
The 4 components that make up the frame are held together with Tabs and Slots, these need to be a tight fit but not that tight that you find it impossible to dismantle them again once test fitted. I would suggest therefore that you adjust the tightness with a file until the fit seems reasonable but not excessive.