19mm..... I THINK
if thats what you were using and it might have even been slightly loose thats probably what it is......... I was either thinking 19 or 21... but a 19mm socket wouldn't fit at all on a 21mm bolt head......
I used a screwdriver and a hammer to knock them out make sure the car is jacked up when you do this.......
I put one on my old car, took it off and put it on this car, so I've messed with H-braces a few times.... if memory serves me correctly.. there is a small bolt head with a metal plate on it that keeps it from spinning so you don't have to use a back-up wrench correct? I work from the inside of the control arm box and take off the nuts, once those are off nothing is holding the bolt in there and it can be beat out.....
you'll have to tap them back in too, the hole and bolt have a fairly close tolerance...
start each bolt seperately and just drive it all the way through on the reinstall. just keep lining it up, you need to line up the control arm, and h-brace, then knock the bolt on through... if your doing this on the ground it might not hurt to have a helper. then thread on the nuts and goto town finding a setup that gets onto the bolt, yet allows the ratchet and socket to fit around the h-brace. I ended up using a 1/2 ratchet and a short impact MAC socket...
while we are on this subject, if you ever have to take it off be careful about ratchet clearance as well... you can start cranking off a nut then the ratchet bottoms out against the other side of the H-brace... then you get to swear a couple times...