In Order To Machine The Brake Drum To Present A Round, Smooth Surface, Calipers Have Been Developed To Accurately Measure The Inside Diameter Of The Brake Drum. It Is Essential To Have A Constant Inside Diameter In The Refinished Drum To Engage The Shoe Surface Evenly. To Achieve A Correct Measurement The Points Of The Beams Of The Caliper Must Be Exactly At The Same Depth Within The Drum. Our Patented Rim Stops Accurately Locate The Caliper At Precisely The Same Depth Below The Surface For Each Measurement. Two Measurements At Different Depths Assure A Constant Smooth Diameter For The Machined Drum. Slidable Pins, Found On Other Brake Drum Calipers, Can Become Fouled In An Environment Where Metal Shavings Abound. If A Pin Inadvertently Slides Inwardly Within The Drum, Instead Of Resting On The Periphery Of The Drum, A Skewed Angle Can Result With Imprecise Measurements.

• Features:
• 0-17.25" Range
• Durable Stainless Steel
• Reads To 0.005" With 0.001" Accuracy
• Inch And Metric Selectable Readings
• Zero Function
• 4.25" Reach
• Includes Protective Storage Case