Insize American Standard Thread Ring Gauge 5 8 18 UNF Class 2A NOGO Series 4121 5C2N 27 mm Insert) Key Advantage: Robust full profile threading 2082250 Key Advantage: Robust full profile threading insert with outstanding wear resistance and stability for coarse pitch ISO threads ✔ Thread Size: 3 4" BSW (British Standard Whitworth)✔ Standard: ISO 529✔ Material: High Speed Steel (HSS) for enhanced strength and wear resistance✔ Thread Form: 55° flank angle for precise and secure Whitworth threading✔ Tolerance Class: Class 2 for a standard thread fit✔ Flute Type: Straight flute for effective chip removal✔ Lead Type: Intermediate lead for balanced cutting performance✔ Cutting Direction: Right hand cutting✔ Application: General purpose threading across various materials The Insize 4121 5C2N American Standard Thread Ring Gauge is a precision NOGO gauge designed for inspecting external Unified Fine (UNF) threads to ANSI ASME B1 Fastener and threaded component verification