Double Zero- Ballistic canopy spreaders are a pyrotechnic device where the base of the canopy is "shot" out in all directions (360*) by small "bullets" attatched to the shroud lines /canopy base by a "gun" which is timed to fire when the chute has reached full stretch but not yet full of air.
Normal parachutes use airflow to "inflate" the chute but sometimes this can prove too slow when there is insufficient airflow going into the chute to inflate it as happens with very slow speed ejections.
The balistic spreader "forces" the mouth of the chute open to catch any availible air in the chute at low speed.
Can be a complicated proceedure and yet another "widget" to worry about when you need a system to work flawlessly 100% of the time.