What size are the bleeder screws on the rear caliper of a 98 Merc?

[formulamojo]

10mm too big, 9mm too small, 3/8 damn near rounded it... Getting

 

[yavapaires]

On my 96 Ex, the bleeders are 10mm. If the bleeders have been changed, they quite possibly could be 3/8. What type wrench did you use to turn them? Always use a line wrench or a 6 point hex to minimize rounding off. If yours are like my front calipers, nothing will turn them, even Vise Grips. In which case, I am looking at new calipers. Yeah, I know they can be drilled out, done that before when I was you.ger and steadier.