This rating evaluates the difficulty of the crux section of a ski descent. It is primarily related to the slope, but also takes the exposure into account, on a scale going from S1 to S7. This system is typically used in conjunction with alpine grades for ski alpinism.
- S1 : Easy route. No particular technique is required to safely descend. For example: a forest route. Well-defined, easy-angled tracks.
- S2 : Large slopes, slightly steep (25°), or hilly routes. Easy-angled undulating slopes and hollows.
- S3 : Slope up to 35° (equivalent to black diamond runs on ski hills). Skiers must be comfortable in variety of snow conditions. Big slopes with low exposure. The ability to make controlled turns.
- S4 : Slopes up to 45° if the exposure is low; starting from 30° to 40° if the exposure is high or if there are narrow passages. Very good ski technique is essential. Big slopes with increasing exposure, or couloirs with limited turning space.
- S5 : Slope from 45 to 50° or even steeper if the exposure is low. Starting from 40° if the exposure is strong. Perfect technique and good headspace are critical. Mountain faces and couloirs.
- S6 : Slopes of 50° and greater if the exposure is high, which is generally the case. If the exposure is not high, short sections of slope at 55°. Slopes with great exposure and seriousness,
- S7 : Sections to 60° or greater, or mandatory cliff drops in very steep and exposed terrain.