Steppers — the driving, marching reggae feel of the late 70s (Burning Spear, Culture, UK dub). Like rockers the kick is four on the floor, but the hi-hat now opens on every off-beat — the "flying cymbal" — and the bass walks in straight eighths instead of leaning on long roots. The cross-stick still marks beat 3, the guitar still chops 2 and 4, and the organ bubble still fills the "an-a" of every beat; the difference is the relentless forward step underneath.
Listen for the open hat answering each kick: "boom-tss boom-tss". It is the same place as the bubble and the skank, so the off-beats get crowded — on a record the organ sits low and the hat sits high.
Practice: play rockers first, then open the hat on each "and" while the kick stays dead straight. If the tempo creeps up you are hearing the step correctly — steppers tunes want to march. Compare the three reggae feels back to back with the kit soloed.