Atami Wilma arrow/flood drippers

Hi all, sorry to sound like a complete moron but i have tried finding the anwser on google but no such luck!

I wondered what the difference is between the arrow and flood drippers on a wilma system, and what one you should use when growing in clay pebbles? The system comes with blue and black drippers and wondered what ones to use.

thanks for reading

the arrow drippers have a very slow feed rate as opposed to the flood drippers that put out a much higher feed rate. the arrows are used specifically if you are growing with rockwool, coco or even soil medium.