SOHC bearing sizes?

[Gabes13]

So I'm gathering up some info for a potential KAe over haul, but I've come across some confusion.

http://www.courtesyparts.com/kb_search_ ... _1420_1428

The link shows 3 different rod bearing sizes for the SOHC:

US=0.08US=0.12US=0.25

3 different rod bearing sizes for 1989-1994:

STD Grade 0STD Grade 1STD Grade 2

and 3 different rod bearing sizes for s13 DOHC:

US= 0.08 US= 0.12US= 0.25

My question is, What does the "US" and "STD Grade #" stand for? and What's the difference?

edit: I mean ROD bearing. Not Crank bearing. my bad.
Modified by pandapants at 9:12 AM 7/3/2009

[maryjane]

its the cut in thousands, how much your crank has been cut down, when you pull the motor apart read the back of the bearings, and itll say std/ .010 ect ect on the bearing size,