The standard for stainless steel reinforcing bars is BS 6744, Stainless steel bars for the reinforcement of and use in concrete – Requirements and test methods.

Various types, strength grades and sizes are covered by the Standard as follows:
Smooth bars, strength grade 200, from 3mm diameter to 50mm
Ribbed bars, strength grade 500, from 3mm diameter to 50mm and strength grade 650, from 3mm diameter to 25mm.