After trying a lot of pencils with mines that break or are too big, with ridiculously small and almost unusable gums, I wonder why it took so long to have this kind of tool, although practice after all, but the principle is not revolutionary!
Please note, 1.4 mm diameter mines are rare to find, it is better to order a box at the same time as the pencil. Personally, I find the whole, also sold on Amazon, including the same mechanical pencil, eraser more spare, more mines a box, is ultimately more interesting, because if you manage to find mines boxes I am not come to find spare tires. On this subject in my other reviews "The perfect pencil?"