I bought a master cylander last week on ebay, it was supposed to be a 19mm to replace the existing one on my 6. Doesn't seem to be a 19, but rather a 23mm. It actually has 23 stamped on the bottom of its case. Sorry I don't have any pics yet. So I was wondering if anyone knows whether the 19mm had 23 stamped on it... And if this is a 23mm, can I use it with a set of stock 6 calipers? Is there any additional installation that is required?

its a 23mm M/C

uh I think thats way too big for stock anything....way too firm.

b

These were used in nonboosted Mercedes cars, and seem to be around. The 23mm will fit with actuation rod modification, but will make the pedal very, very hard on a stock car - really too hard to effectively modulate.

They will work fine if you have large (ie turbo 911) brakes on the car, but they really are only for that use. Stick with the 19mm for a street car.

I'd recommend measuring the bore to be sure. I never trust numbers stamped or cast on parts anymore. If it is a 23mm, as already noted you will also need the alloy steering support or bang a big dent in the stock steel tube one on your car if it is still there.

what they said. WAY toooo big for M calipers and 914 rears....

great for 4 psiton calipers on all 4 corners

I agree with measuring it to be sure...
many of these are not what the number says.
I think I had 19's that were stamped 17, or vica-versa....

measure to be sure
and if it is a 23 then resell it and get a 19
brant

Thanks everbody! I'll measure it tonight to be sure.

What did you find?
Was it just a casting number or the bore size?
A 19mm has an actual bore size of .750", yep 3/4 inches, actually an inch part.