"At first, I was worried. Disassembling my mechbox, I realize the 120 spring is inches longer than my stock spring, and more rigid too. It was a near impossible task for ME to install it. So did I take it to a professional and pay good money for them to do it? Nah, I just took it over to the stove, and heated up one end. This allowed me to compress it and shave of some inches. Admittedly this can lower your maximum FPS, but it worked like a charm. Once installed, I shot around 370fps with .20g's. "