This is a ceramic dome tweeter with a neodymium magnet.  I picked these up based on the manufacturer’s claims of low distortion, extended response (to 30 kHz), and the compact mounting dimensions.  A plastic mesh grid covers and protects the dome.  Its the center tweeter shown below.

Here’s the first unit frequency response

Very smooth, and extended to 700 Hz, but a combination null / peak at the top end.

The distortion measurement

A little higher than expected.  Other tweeters and systems that I will be showing have the harmonic distortion as low as 50 dB below the fundamental.  The distortion is rising below 2 kHz which limits the crossover frequency and slope to be 2.5 kHz at 3rd order.