When I first picked up this 0.4mm Zebra Sarasa gel pen, I was disappointed by how scratchy it was. I had been using the 0.7mm Sarasas for years and had never had any problems with them. However, first impressions can be deceiving. As I have used this pen more, much of the scratchiness has gone away, although it is still far from being as smooth as a Pentel Slicci or Uni-ball Signo DX.
The 0.4mm version is a smaller, thinner version of the 0.7mm. I do not like the rubbery, hard, slightly sticky grip; it has accumulated a few black smears on it that will not come off and it feels as though it would attract dust and lint as well (I've just tested it by rubbing it on my cat's back and it did attract a few cat hairs).
0.4mm Sarasa (top) and 0.7mm Sarasa (bottom) compared.
I cannot resist comparing the colour of this pen to that of the olive green Pilot Hi-Tec-C that I reviewed a few days ago. As you can see on the written review, the Hi-Tec-C olive is a bit darker and considerably greener than the Sarasa olive. Being a fan of green inks, I prefer the Hi-Tec-C olive, but the Sarasa's version may be more true to the olive colour (I'm not an expert on olives so I don't really know).
The 0.4mm Zebra Sarasa is not a bad pen, but if you are looking for a good fine-tipped retractable gel pen, I would be more likely to recommend something like the Uni-ball Signo RT, which writes more smoothly.