• Accurately milled steel blades
• Designed to check both internal and external thread forms
• Marked with nominal size on each blade
• All blades fixed in a steel sleeve
• Screw cutting gauge included
• 801, 804, 806, 809 available in Retail Packs.
Note: SI (System International) metric blades should not be used to check ISO (International Standards Organisation) metric threads due to interference of the thread forms; but ISO metric blades can be used to check SI metric threads.