Some Honda uses M12x1.25 and S2000 uses M12x.1.5
What does 1.25 and 1.5 stands for? depth?
can I fit both on same car??

TIA!

 

Won't fit. They have different thread pitches. My understanding of how these things works is this:

1) The first number (12) is the diameter of the threaded portion (not the head, so it doesn't tell you what size socket to use.)

2) The second number is the thread pitch - in metric bolts, it's how many mm seperate each thread. The higher the number, the coarser the thread.

Bolt trivia - you only need the first six threads to get the full fastening strength of the bolt.

 

Also, for metrics, if the pitch is not indicated, it's a coarse thread (1.5).

Sometimes, the bolt will be listed as M12x1.25-40. The 40 indicates the total thread count. From this, you can calculate the bolt length: 40 x 1.25mm = 50mm.


EDIT: Or does '40' indicate 40mm thread length?

 

"stem" length??

 

Look here:
http://mdmetric.com/tech/tic1e.htm#helpnote