The Cretacolor Ergonomic is a 5.6mm leadholder with an unusual grip section. The barrel has a zig-zag section which is claimed to be ergonomic. Artists have long applied tape and padding to make leadholders more ‘holdable’, and this instrument attempts to anticipate that challenge.
The ideal grip is obviously a highly personal choice, and the Ergonomic is worth mentioning for those on a quest to find that grip. (I’ve found the Ergonomic good, but not quite right for me, while others love it.)
What can you do with it? It can use a huge range of graphite, compressed charcoal, wax colour leads, sanguine and sepia leads, chalk, or even a ballpoint adapter. Here is a nice Cretacolor lead set I found. Unfortunately, I broke a lead on the way home: