On my vehicle the "O-rings" were molded on the tubes, and still in good shape (soft). I just re-used them.

How many miles are on the X Doru? Ill double check mine when I get home tonight but I think mine were fine too. I was just thinking preventive maintenance but if most are reusing than I should be fine too.

If the molded o-ring on the tube is like the molded o-ring on a Disa valve for a 3.0 after a while they loose their abilities to seal.

The cheap fix will be to scrape off the molded o-ring and replace with regular o-ring of the appropriate size.

I ordered 8 new tubes to do mine... sucks as they are kind of pricey when you multiply by 8. In to see if there actually is a set of seals for these available.

I believe the O-rings are removable and not molded onto the tubes. Ill verify tonight and will post. But if they are removable replacing them with ones similar Im sure wouldn't be an issue especially if the tubes are still in good condition!

Update it appears that the O-rings are molded into the tube as upallnight stated! Could be possible to replace them as he mentioned as well.

It's NOT the same rubber compound. These have higher heat tolerances than the DISA molded O-ring.

Probably why mine are still in good condition at its current miles. It could have also been replaced by the previous owner but uncertain.

The sparkplug tubes are good until they are cracked IMHO. For the tubes to crack, there should be either a higher than normal engine temp, or consistent accelerated temp differentials, I believe. Or wrong installation.