Sat variable velocity device VVD

new speed adjust device available
comes with:
-hi strenght steel piston+piston head and adjust screws
(reduce the spring power from 100% to 70%)
-screwdriver set with steel extention rods
(ideal with every barrel lenght)
the adjust should be done after a single shot and wthout magazine
ideal use with marui/g&g/g&p/king arms aeg etc.....