ZEV Technologies high quality round wire recoil springs are color coded for easy identification. No more counting coils or guessing if you have the correct spring. The red spring is 14 lbs and is ideal for hot 9mm, 40 S&W or 45 ACP. Blue spring is 12 lbs and ideal for standard velocity 9mm. Coating on the spring will typically last 3000 cycles which is our recommended life of the spring. ZEV recoil springs will work in captured and uncaptured guide rods. When using a captured guide rod you will also need the ZEV spring retaining washer.