OEM Rb26 Piston Flats Number Significance

[dylanc]

Hey guys,

Was curious what the numbers on the top flats of the Rb26 pistons mean/signify? I have a range of numbers on the piston flats, what does this mean, and are they different OEM pistons?

Cyl 1: 2, 05U, 06
Cyl 2: 2, 05U, 06
Cyl 3: 2, 05U, 05
Cyl 4: 2, 05U, 06
Cyl 5: 1, 05U, 05
Cyl 6: 2, 05U, 05

Sample photos so you know what I'm referring to:

[dylanc]

Answered my own question, the 2 indicates piston grade and they are 0.1mm oversized, and the bottom represents piston pin grade. Any ideas the difference between 05 and 06 piston pin grade?

Cheers