Mitutoyo 137-219 mechanical extension rod type tubular inside micrometer offers the ability to measure a wide range of inside dimensions with exact precision. It includes a set of solid extension rods to measure a diversified range of inner dimensions of cylinders, rings, and parallel surfaces with high accuracy. Slow head travel provides fine measurement position, while a locking clamp holds measurements in place for easier reading. The extension rods have knurled collars for easy, secure installation and removal.