DS18 has a huge variety of audio drivers. A lot of these drivers require external throats to purchase. The DS18 pro - HA 100 is a four bolt throat that's 2" in diameter and has a depth of 4.84" to fit most 4 bolt pro audio drivers.
WARNING:These products can expose you to chemicals which are known to the State of California to cause cancer, birth defects or other reporoductive harm. For more information go to P65Warnings.ca.gov