0.82" DIA. X 0.15" MINI TONE TRANSDUCER

I bought them for use as drum triggers for my electronic drum set, but they are not very sensitive. At the highest sensitivity on the drum module they return values up to only about 50 out of 127 when I slam them on the table. For applications such as this go with the lone, un-encased piezo element and get some large sticky rubber feet to encase it back and front. That works great. I will be ordering more of those other items, but not more of these ones!

This part is a mini dynamic speaker with 28 ohms of DC resistance for the voice coil. Also, the perforated metal backside is the primary sound output side.