Open source FPS reducing tuning cap for the nexus pro blaster. Not extensively FPS tested at this time but should drop your velocity by 20-30 FPS.
Print with supports.
To install unscrew the stock cap and twist off. Remove the spring and place it into the printed cap. Twist on the new cap. The flanges should line up with the ones on the buffer tube of the blaster. A screw is not required to keep it in place.
The author hasn't provided the model origin yet.