Connecting Rod Bearing Selection: Notes

Each connecting rod falls into one of four tolerance ranges from 0 to 0.024 mm (0.0009 in.), in 0.006 mm (0.0002 in.) increments, depending on the size of its big end bore.

It's then stamped with a number or bar (1, 2, 3, or 4/ I, II, III, or IIII) indicating the range. You may find any combination of 1, 2, 3, or 4/ I, II, III, or IIII in any engine.