taco eater :
Adam Riggsby from Allston, MA United States
this o-ring is sick. kinda hard to install, but it is part of Tomos patented "2 o-ring combination" that stops the black wheel of death. The other o-ring is the 30mm x 1.5mm o-ring. That one is way easier to install.
Either way, if you got the black wheel of death, replace the o-rings and be happy knowing your transmission fluid is staying in your transmission.