The modifications that have been developed in order to adapt the Sonigage to the quick inspection of Diesel cylinder liners are described. A method of introducing ultrasonic vibrations from a conventional flat‐crystal probe into a curve surface and an adaptor for determining thickness by interpreting the harmonic responses have proven to be valuable in expediting this type of work. In the hands of an experienced operator the technique can be made to yield much valuable information concerning the relative homogeneities of the castings.