noodels

stuck a Prowin in my Star UMP & went from 300 to 350 fps, so expect an fps increase + better fps consistacey. One more thing you must remove the top frontmost screw from the gearbox to get the hopup lush with gearbox. Aleast I did with UMP.

order springs directly from PDI , thats what I did In fact I order everything PDI from PDI home page.

AEG spring diameter = 15 mm VSR-10 spring = 10 mm Lylax APS spring = 12 mm PDI SS 2000 , 3000 , 4000 , 5000 springs = 13 mm. hope this helps PDI VSR-10 springs = 11 mm

As for adding a susat Armycode sells the mounting rail for that sight separately, check WGC ( mounts & rails )