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Whats different about the m675?
Does one have the finned pads
M666 are the newest style lever with the reservoir in line with the hose, M675 is the old style lever with the perpendicular reservoir.
There may well be left and right handed levers as I don't think Shimano make flip- flop levers i.e. can fit the lever on the left or right without re-routing the hose.
Check out techdocs.shimano.com for more info.
The M675 are the newer version. As far as I can determine there is no difference. One ad says they were formerly called M666. Both have finned pads.
There's every chance they had to rename them due to complaints from Iron Maiden fans or Christian Fundamentalists.
[i]M675 is the old style lever with the perpendicular reservoir.[/i]
That was M665.
cheers ppl.