This lead writes super smooth. The 0.7mm isn't too fragile. I had to shift to a
harder lead from the standard (HB?) in my 0.5mm mech pencil, but don't have much
of an issue with the Eno neos (blue, red and yellow so far). If you are very
heavy handed and leave a lot of lead protruding from the point of the pencil,
you will break this lead quite frequently. The Pentel Graphgear 500 has an
extremely short advance, which works great with the Eno lead.
My gripe with the yellow is that it is way too light. I got it for note taking.
it is pretty useless for anything other than heavy filling or highligting. The
yellow is very bright, but the color is too soft.