This is the description for aero j-style pickups: Type 1, Std (Neck/Bridge) - Reviewed in the March 1999 edition of Bass Player Magazine, Aero's J Bass 4 String pickup won a "Top Tone" award. The complete comment, "Heavy lows, distinct upper mids, and round top that's cool for fingerstyle rock, blues, and country. (And '70s-style funk.) Broken-in vibe that's fun to play. On tape, pickups have big bottom for a J, although the tone can get a bit thick." Type 4A - Type 1 pickup with four 1/4"OD pole pieces. The pickup has a narrower field than the Type 4, but has exposed pole pieces. Ok, what does "narrower field" mean exactly???