The Kuru Toga, aside from being a genius design, is solidly built and comfortable to use. There must be billions of these sold...so I am just one of many, many, many, (well, you get it) folks that appreciates it. I like the blister pack with the pen AND supply of leads. The 0.5mm size is, I think, the most popular overall...leads have decent strength so there’s low breakage. As I recall this is sold with an HB hardness which writes a medium gray. I usually prefer a 2B or at least a B which gives a much darker line. Highly recommended. There are models of the Kuru Toga that revolve the lead at twice the rate (this one is standard) which may work better for those that write in cursive (see the Kuru Toga Advance, etc.). Pretty much any Uni product, like Pentel, is a solid product. Buy without fear.