Proper thickness for platter mat Technics 1200GR(2021)

The stock mat is 3mm and it is OK.   I have also learned that many shorter cartridges will not be able to be levelled because the arm height dial runs out of travel.  

I tried many mats with my GR and by far the best is the Herbies with 4mm thickness.  Great damping without too much and the additional mm lets shorter carts be dialed in perfectly.  

Worst by far was the achromat which blurred and ruined bass response. 

To test the effectiveness of mats play music at high volumes and listen to the bass- beats and sustained.  Listen for good definition and clarity of notes.  Also listen to the midrange and check for coloration.  

The best mats will dampen the arm resonance and let the bass sound sharp and focused and leave the midrange nice and clear.  

I have the Achromat for my SL 1200 MK2 and have been very happy with it.  While the table has VTA, you may not be able to get the arm level with a thinner mat.  I haven't experienced any negative consequences as a result of using the Achromat.  I use a fairly heavy weight with it, so maybe that helps avoid the issues another poster mentioned.

@big_greg  - Hi Greg. Do you have the Achromat that is specifically designed for the SL1200? How does it fit? Does it have a channel cut out of the bottom to fit over the ridge on the outside edge of the SL1200 platter? Or is the diameter small enough to sit inside of the ridge on the outside of the platter?

Just curious because it would seem you would want the aftermarket mat to be in contact with the whole platter. A stiff mat that did not fit either inside of the raised ridge, or have a channel to accommodate the ridge, would not sit flush against the platter, correct?

BTW, with my Audio Technica AT-VM740ML, I cannot get the VTA correct using only the stock mat. The VTA adjustment bottoms out before I can get the tonearm exactly level. It's close, but I would like to have a little adjustment on either side of level to test different VTA settings.

@reubent Tom, it's been a while since I bought mine but it is the one for the SL 1200. It comes with adhesive to make it lay flat on the platter so I don't want to pull it up to look at the bottom. Works great, and the fit is good. I know there is a version that has a lip and one that doesn't. I would contact Funk Firm and ask them if it will fit your table.

Thanks Greg...