These are bore gauges that automatically self-centre via a centring bridge. They offer you the following benefits: 

• A long plunger stroke gives you amazing accuracy. -Interchangeable washers 0.5mm thick are supplied as standard accessories, so you can enable setting in small steps.
• Contact points are carbide (>18 mm range), giving you high durability and wear resistance.
• A large grip reduces heat transfer from the operator by 50%.