Precise Measurement - Capable of Measuring Hole Depths up to 42mm (1-11/16"), with a range of approximately 14mm (9/16"). Standard Compatibility - Fits All Indicators made to AGD standards, ensuring wide applicability in various measuring tasks. Secure Clamping - Features a 9.5 mm Diameter Hole for firm attachment, providing stable and accurate measurements. Versatile Functionality - Designed to Measure the Inside of Holes and other hard-to-reach areas, enhancing measurement capabilities. The Standard For Excellence - Proudly made in the USA, Starrett combines over 140 years of American heritage and innovation with globally sourced materials to deliver exceptional quality tools and products. The Starrett 670B Indicator Hole Attachment is a precision tool designed for measuring the inside of holes and other hard-to-reach areas. It has a range of approximately 9/16" (14 mm) and can measure hole depths up to 42mm (1-11/16"). This attachment is compatible with all indicators that adhere to AGD standards, offering versatility for various measurement tasks. It features a 9.5 mm diameter hole for secure clamping to the indicator stem, ensuring stable and accurate measurements. The 670B's design reflects Starrett's commitment to quality, offering durability and functionality for professionals seeking reliable measurement solutions.