Meggitt A/S PZ26 (NAVY 1) Hard Relaxor type PZT Hemisphere Focusing Transducer has a resonant frequency of 6.7MHz. The size of the Hemisphere Dome is about 19mm and Radius is 13mm. It has a 3.5mm center hole and the material is about 0.35" thick. The ceramic focusing transducer is new and was made for a medical device. No leads have been attached and you must be careful when soldering leads as they are fragile and will break if you drop them or use too much force when attaching leads. Sorry no other data. Retails for many times our price!