It sounds like you’re describing a lateral extensometer used for measuring the lateral extension (or strain) of a 150 mm diameter x 300 mm high cement concrete cylinder during compression testing.  Designed for 150 mm diameter x 300 mm high cement concrete cylinders. Two Movable Frames Pivoted at one end to allow precise measurement of lateral deformation. Dial Gauge Measures lateral extension with a resolution of 0.002 mm and a range of 10 mm. Removable Spacer Strip Used for initial calibration/setting of the dial gauge. Mounting Mechanism Secured to the specimen using screws. Packaging Supplied complete with the dial gauge in a wooden case for storage and protection.