Size

 Flatness of working surface & parallelism of opposite surface

Squarness between working suface 

 Tolerance of h.w between a matched pair

 160*25*16

 1.5

 20

 1.5

 250*40*25

 2

 30

 2

 400*63*40

 4

 40

 4

 630*100*63

 6

 50

 6