Bough this along with the SS Guide Rod for my CZ SP01. The guide rod is beautifully machined without burrs or machining marks with a mirror like polish. It was a little more cumbersome to install using the factory, flat wire spring - just requiring a couple more seconds of patience to prevent binding but not the impossibility that some reviews have so to eluded. Functioned just fine with the flat wire spring. I did, however, upgrade to this round wire extra power spring as well, and that made a huge difference in reducing muzzle flip; getting back on target; and keeping all of my brass at five to six feet from my shooting position. I shot 124gr WIN 9mm NATO @ 1200fbs, 115gr FIOCCH 9mm @ 1200fps, and Speer GOLD DOT 124gr @ 1235fps. It was a little harder to install from a tension standpoint due to the extra four pounds and extra length but otherwise smoother than keeping the flat wire spring from binding. My guess is that's why the factory guide rod is made out of a more flexible DELRIN material, so that it will flex with the flat wire spring as well as to navigate the unusually long dust cover / guide rod seat at the bottom of the slide. In conclusion: a seamless upgrade with the factory, flat wire spring with better aesthetics, and a performance and accuracy upgrade combined with the extra power M*CARBO round wire spring. The reduced diameter in the center third of the guide rod was a very unique, engineering solution to the potential binding issues mentioned above. Well done M*CARBO!