D.I.D."s 520NZ chain is a non O-ring chain with solid bushing and quad-riveted pins. D.I.D."s SDH high-tech pin treatment forms an extremely hard chromium carbide layer on the pin"s surface while maintaining a softer inner core. SDH treated pins have extreme impact strength while adding outstanding shock absorption. The SDH process creates a chain with superior wear resistance, outstanding anti-oxidation properties and performs well in dusty and muddy conditions.