One of the finest springs money can buy.
These Variable Pitch sprtings (also called Non-Linear or Progressive) are hand made in Japan from Silicon Chrome Steel and have one section of slightly tighter coils to reduce the initial stress on the gears and piston.
They are generally shorter and stronger than most Non-Linear springs so give a more stable power output and last much longer.
These are rated as a percentage of the standard Tokyo Marui springs (0.81J) and are listed with their approximate Joule rating and the equivalent fps with 0.2g BBs.
As with all springs, the precise energy output will vary depending on your exact setup so if you're unsure as to which one would be most suitable, feel free to drop us a line.
We don't generally recommend using very weak springs for most builds, a stronger spring with short-stroked gears is a much better option to achieve under 350fps.