Red Silicon ones are what I used thick as possible.
Get your size here (ebay), remember not too tight or they will over time dent the tube glass, use 1 2 or 3 per tube. And remember the smaller tubes input, phase splitter, drivers are the ones that can be more micro-phonic.
To test which are micro-phonic, raise the volume to normal (no music playing) and gently flick each tube with your finger nail, and you’ll hear the micro-phonic one/s in the the speaker quite easily.
https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=Silicon+O+Rings&_sacat=0&LH_TitleDesc=0&_osacat=0&_odkw=Silicon+%22O%22+Rings
https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2334524.m570.l1313.TR0.TRC0.A0.H0.Xred+O+Rings.TRS1&_nkw=red+O+Rings&_sacat=0&LH_TitleDesc=0&_osacat=0&_odkw=red+%22O%22+Rings
Forget about expensive BS "audio" ones.
Cheers George