I noticed when I used my Dubro glo plug wrench that it was not fitting onto the glo plug head securely on my SAITO 125. When installing the plug, it's shoulders were rubbing too tightly against the cooling fins causing the plug to go in slanted. Luckily I noticed it right away otherwise I too would have probably cross threaded the plug. The wrench shoulder is very thick so I was able to dremel it down to the point that it fit properly into the glow plug slot and now I can remove/install without any issues. However when I used this same wrench on a Saito 56 there was all kinds of room around the driver end and it never presented an issue. It sure did on the 125. So beware.
Best,
Gary A