Procomp Electronics rocker arm adjusting nuts are high-quality Polylocks designed for full roller rocker arms. Made from heat-treated, premium-grade 4140 Chromoly steel, these adjusters provide 190,000 psi tensile strength for the utmost in reliability. Precision CNC-machined threads to ensure optimum seat pressure, flush-machined set screws for proper contact on the studs, and, best of all, they don't require any special tools for installation.