It seems excessive to write a review for mechanical pencil leads, but "good things should be said": forget anything else. They are the best that exist. And I say this having tried almost everything available in 0.5/HB, including Faber and Pentel...
You will have a little difficulty finding them - few stores carry them, which is why I order 2-3 boxes each time through Skroutz - but you will be rewarded with flawless, pleasant, smooth writing that does not scratch the paper and zero breakages. Highly recommended.