PILOTHi-Tec-C Coleto Mechanical Pencil Unit for 0.5mm Lead (LHKRF-18H5) 2 set

Super useful! Now I don't have to have a separate pencil and pen, which saves space for someone who carries a lot of pens. There's a bit of a learning curve as you get used to it but not much. Just gotta get that muscle memory.