A friend had two of these and gave me one to try. It does not improve LP
playback on my turntable (Nottingham Analogue Mentor), but the manufacturer
recommends against it on my platter (synthetic stone).

It was originally designed as an upgrade for the Linn felt mat and it
apparently works very well on metal platters and others. Go to
extremephono.com for additional information.

I have the donut-shaped version, which retailed for $32.00 plus shipping.
Mine was used just to try it out.
Will sell for $25.00 plus actual USPS shipping (to be determined).

Please email if interested.

Thanks,
Steve