A2 just means that it is normal Stainless steel. A4 is acid proof stainless steel.
They are generally available in strength ratings(property classes) of 70 and 80

A2(A4) - 70, tensile strength = 700N/mm2
A2(A4) - 80, tensile strength = 800N/mm2

8.8, tensile strength = 800N/mm2
10.9, tensile strength = 1000N/mm2
12.9, tensile strength = 1200N/mm2

But there are more factors to take into consideration before using stainless bolts.