The Zev Technologies Guide Rod Reducing Ring ring allows you to run a standard diameter Glock guide rod and spring on your 4th generation Glock. The Guide Rod Reducing Ring allows the use of aftermarket Gen 3 guide rods and recoil springs on your Gen 4 Glock for optimal performance and customization. FeaturesAllows use of narrower diameter Gen 3 guide rods and recoil springs on Gen 4 GlocksIncrease your aftermarket guide rod and recoil spring optionsMade in the USA DISCLAIMER: This product is not manufactured, authorized, endorsed, or warranted by GLOCK. GLOCK does not warrant or represent that this product is compatible with GLOCK pistols.