From Aguilar:

Using our dual ceramic bar design, the DCB 4PJ introduce a new and unique voice for PJ style basses. These passive, hum-cancelling pickups are engineered to deliver higher output versus traditional passive pickups – and without any shift in frequency response common with overwound or active pickup designs. Characterized by their full-bodied tone, rich sustain, and smooth dynamic response, these pickups are a great choice for any bassist looking for a new dimension in sound.