We have three typographic scales that apply to the following breakpoints:
Scale 1: 320 & 600
Scale 2: 768 & 960
Scale 3: 1200
‘H1, H2’ numbers are used when semantically correct. If not, use ‘S1, S2’ and so on to describe the size.
There is a preferred weight for each size, but other weights can be used where appropriate to help the hierarchy and structure of the page.