I mod many blasters, including strongarms, and this worked well as an upgrade spring at a cheap cost. If you take out the air restrictor, that coupled with this spring will make you a solid sidearm. On the Chronograph, it increases fps by almost 6 fps. The only problem that I have with this one that prevents it from getting 5 stars is that mine didn't go into the plunger tube without some extra force and a tiny bit of bending. When I looked again, it was a bit shortly sized. I don't know if mine was just a manufacturing bug or whatever though. All in all though, for only 5 bucks, it is a great spring.