Did my first transmissions fluid / filters change yesterday. Insane. Never got the vent plugs removed. 1/4" seemed to be the size but had a tad of slop. Thought it might be 7mm but didn't have one. Broke three 1/4" allens and stopped with my fourth and last one as it was bending towards breakage. If I can know the correct size (Hydro-Gear tech support person, my dealer and a competing dealer, did not know the size :thumbsup, I'll buy a stubby like those that insert to drivers and put a wrench to it. Only thing else I know to do is hit them with a torch which I really don't want to do near the belt and plastic pulleys. The two filters took close to 5 hours to remove. I went through 7 filter wrenches, two of which were only 2 1/2" diameter. They just wouldn't bite, even with some mods I did to them. Ended up using the filter wrench style that resembles a large set of channel locks. Took forever to fill the 2 trannys due to the burping through the reservoir process. So anyhow, does someone know the correct allen size for the vent plugs? Thank you.