The Rival Arms Heavy Guide Rod Assembly is designed to be an upgrade to the factory guide rod. Polymer can fail from cracks or breaks and is susceptible to accuracy robbing flex. The Rival Arms design addresses these issues and provides a lifetime of reliable service. FeaturesPremium spring in stock weightFully assembled Optional CNC-machined tungsten for added weightNo gunsmithing required 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.