The Blueline mics (as many others) are modular system mics. That means a complete and functioning microphone consists of one of your choice of several different capsules, depending on your needs, plus an eletronics/preamp module. You need both components for the thing to work. The modular arrangment allows you to save money by buying one preamp and several capsules, changing out the capsule on the preamp to fit the needs of the moment, rather than buying a set of complete microphones.
