Fox Suspension Fork Volume Spacers.

Features:

Changing volume spacers internally adjusts the amount of mid-stroke and bottom-out resistance
More spacers = less air volume, providing a more progressive spring curve
NA are first-generation negative air spring forks using the transfer rod to equalize the air pressure. NA2 is the second generation where the transfer rod is removed
Specifications:
Model: Fox Float 40 NA2
Volume: 10cc
Included: 5-Pack