MM5.4w Humbucking quad coil 5 string MusicMan®-style bass pickup:

This is a quad coil pickup designed to allow a silent single coil switched operation for either the front or rear coil. It can also run parallel or series, depending on taste.

The industry never really adapted a standard for this style of pickup, and as a result they are available in 3 different spacing and cover combinations.

 The 5.4w is Larger shape with ears and wide spacing. These will fit Lakland® and other basses with wider spacing.