(I have noticed that the central 1.5mm divider bumps up the material used costs quite dramatically.)
The bobbin has provision for up to 44 pins/tags (22 per end), so can have up to 44 wires!
I use "Fine Silver Rectangular Wire 2.00mm X 1.00mm Fully Annealed" from cooksongold.com - order code = KSF 0200 - in 12mm lengths.
http://www.cooksongold.com/Wire/Fine-Silver-Rectangular-2.00mm-X---1.00mm-Fully-Annealed-prcode-KSF-0200
With the "Strong and Flexible" in sintered Nylon material the overall surface finish tends to be a bit bobbly, so when fitting the tags may need to be heated. For the "Frosted Detail" in UV Acrylic they should press in directly (but the material is not as robust as the Nylon).