[Shazaam!]

HH pads originally meant EBC pads, but I think other brands may use those initials. You will know when you take them off, if the writing is still legible.

There is a two letter code mandated by the DOT, and painted on all street legal brake pads to give some indication of their ability to resist fade. Because of the wide range involved in each letter, it is only a rough indication.

A HH code brake pad material has a normal coefficient of friction of 0.55 or higher, and a hot coefficient of friction of 0.55 or higher.