A Blade Micrometer measures the outside diameter of workpieces which have narrow grooves. "T" slots and other features. 

These Starrett Blade Micrometers are designed for fast, accurate measurements. The balanced design ensures perfect balance, handling and better readability.

Features:

• Measuring Range: 4-5"
• Graduation: 0.001"
• 0.030" / 0.8mm Blade Thickness
• 0.30" / 8mm Blade Depth
• Non-Rotating Spindle
• Includes Setting Standard