Block level, We are dealing in block level of RSK make. Grade AA, A and B are manufactured and inspectedunder the JIS B 7510 standard.( See P5. for further information on each grade. )· Grade AA has ±0.2 scale all range accuracy in the main bubble· Grade AA and Grade A have an insulating material which prevents heat transfering.· Grade AA and Grade A have a bubble chamber in which the length of the bubble is manually adjustable.