Pairs of conical probes are specially designed for Digimatic, Dial and Vernier calipers to quickly measure centerline distances. Due to the fact that the smaller attachment is .375" in diameter, and that the conical points are .375" apart when closed, the centerline gages do not measure distancesless than .375" when the caliper is closed with the attachment installed. The centerline distance is read directly off the caliper without a conversion factor. Each probe has two small holding bolts and the attachment is supplied with an Allen wrench. The probes are black oxide finished, and arequite durable for the required measurements. The 60° conical probe snugly fits into the holes, and takes guesswork away from center distance measurements.