Over the winter, I converted my foam tip ear buds to the custom silicone pieces. We published a piece about it in Speed News:

Speed News Vol. 6 Issue 1 February 2017 - I

I just had the chance to use them over the weekend and, man, what an improvement and certainly money well spent. I just put a little spit on them and twisted them into my ears. They blocked out all the raucous noise from my car and those around me and they allowed me to turn down the radio volume so I didn't get blasted when my spotter chimed in.