Both. Officially, the kevlar helmet had replaced the steel pot, but units received them gradually. I was issued the kevlar in Boot Camp (Nov. 1985-March 1986), wore the steel pot at Combat Engineer School (March-June 1986), and when I checked in at my first unit, they still had the steel pot, but received the kevlars a few months later. Infantry units had already been issued the kevlars, IIRC. Pretty much the same with the M16A1/A2 and 1911A1/Beretta M9.