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This doesn't look like it has been installed properly. The diameter of the tube in the bottom part of the clamp looks larger that the diameter in the top part. Which would explain why it has snapped.
The ISO standard for critical bolt failure on seatpost /handlebar /stem is minimum 20% above manufacturers stated max.
chiroshi-
That's after it snapped though. I was holding the post while tightening and could feel it move up.
It's possible but unlikely that it wasn't flush with the seat tube. I don't think I've ever removed the clamp so fail to see how it could've not been flush in x years, especially given the bashing last weekend.
I'm putting it down to old age, lots of 'during race' use where it wouldn't always have been torqued with a torque wrench, etc.
I've got a spare clamp on for now, until the Mason replacement arrives.
hippy
Mine is different, an older version, it doesn't have the little steel barrels.
I'm surprised I didn't break it out on the road when fucking around after crashes and stuff to be honest. I stupidly gave it 5Nm instead of 4Nm with a new post installed and I felt an odd pop. It had cracked across the front.