Often, unfairly derided by purists, these little humbuckers produce a powerful tone with more focus and clarity than a standard humbucker.
Two thin narrow bobbins, packed with hand-wound wire coils over a bar magnet. One with the little screws, the other with a chunky bar of steel - its not designed like a normal humbucker and doesn't sound like one either. Slightly mismatched coils produce a clear aggressive tone with a broad sonic spectrum. Versatile and responsive enough for all types of music.
All my minis can be under-wound up to 10% for clearer tones and hollow bodies, or overwound up to 5% for more dirt!