Principal of a guide rod...It's as simple as this: Take a spring, and compress it between two of your fingers. What happens to the middle?...It bows, right? Now say that spring has a rod running through it. No bow, and no bow means a smoother opperation. That's all. Some people claim that it adds stability, reliability...some say it shouldnt be in the gun at all because one of the one handed methods for retracting the slide cant be done with a guide rod in the gun. It's a stupid debate really. If you are a tactical military opperator...and think that maybe one of your arms will get blown off, and you might have to manually cycle your weapon with one hand?..then leave it out...Otherwise, I say it's good to have one. I'll get off my soap box. --HD