This is a case of four 1.3 mm B leads. The soft thick lead is useful for filling in sheets that are read by optical character recognition (OCR) such as "scantrons" or "bubble sheets." It is also ideal for drawing and writing notes.
This lead is pretty good. There are better 1.3mm leads (*cough* Campus 1.3mm 2B
*cough*) But this one does work. I like the 1.3 mm size for woodworking as it
leave a nice cut line but never needs sharpening. Softer leads work for my
heavy hand and really are better for working on rougher surfaces (yes they wear
quicker, but have less of a chance of breakage). There are only 4 leads per
tube (as opposed to Campus' 16) so make sure you note that when figuring out