SPI 30-486-5 Groove Master Attachment, Metric Size 4, 18 mm

Features:

• Highly effective caliper attachment for quick and accurate measurements of internal and external diameters of retaining ring grooves, o-ring grooves and undercuts.
• Precision machined from steel, hard chrome plated for extra wear resistance.
• Measures internal grooves from 0.200" up to the capacity of the caliper.