broncobowsher
Contributor
To further answer the original question, page 113 of the owner's manual lists the types and what they can do
https://www.shearwater.com/wp-content/uploads/2018/05/NERD2-UserManual-DocRevD.pdf
https://www.shearwater.com/wp-content/uploads/2018/05/NERD2-UserManual-DocRevD.pdf