Slice Turn Metric
From Speedsolving.com Wiki
The slice turn metric (STM) is a metric for the 3x3x3 where any turn of any layer, by any angle, counts as one turn. This differs from HTM in that a slice move counts as one turn, not two. And it differs from the Snyder Metric in that it does not include anti-slice turns, imbalanced anti-slice turns, nor compound multi-layer slice and anti-slice turns.
Cube rotations do not count as turns. STM is a very popular metric for those who use methods with many slice turns (such as Roux) although the official Fewest Moves event uses HTM.
The following algorithm would count as 10 turns STM: r2 U R' U' M U R U' R' r' (an edge 3-cycle on the front face).
