Abstract: Apparatus for measuring wall thickness of a container having an open mouth includes a gauge indicator mounted on a support base, and having a first tip and a readout that provides an indication of position of the first tip. A probe arm includes a rod mounted on the base, a second tip pivotally mounted on the rod, a sleeve slidable on the rod, and a link connecting the sleeve to the second tip such that pivotal position of the second tip on the rod is controlled by position of the sleeve along the rod. The second tip is movable between a first position at which a container mouth is receivable over the second tip, and a second position at which the second tip internally engages the wall of the container in opposition to the first tip such that the readout provides a measure of container wall thickness between the first and second tips.