Short Answer: 8mm To make my life easy I pulled the stock bleed screw out and tossed it. I replaced it with part # SB7100sss from www.speedbleed.com. It's a bleed screw with a check valve in it. Open it once, put a hose on it (they have a great bleeder bag combo on the website), pump the clutch until the new fluid comes out clean (make sure you keep the resevoir full-Castrol, GTLMA Dot 4 ), remove the bleed bag, tighten the bleed screw, put the protective rubber cap on it(comes with the new bleed screw). Repeat every two years (same for the brake system). Nice, neat, clean. The part # above is for the stainless steel version (why not?) or they do have plain steel, just drop the last two ss from the part #. Stephen Vin 3601 To address comments privately to the moderating team, please address: moderators@xxxxxxxxxxx For more info on the list, tech articles, cars for sale see www.dmcnews.com To search the archives or view files, log in at http://groups.yahoo.com/group/dmcnews Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/dmcnews/ <*> To unsubscribe from this group, send an email to: dmcnews-unsubscribe@xxxxxxxxxxxxxxx <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/