The gradings used on PisteHors.com is based on the American Yosemite Decimal System. The first three grades are basically walking routes. The two higher grades are still largely walking routes but will involve some climbing skills and possible rope work.
Moderate - Marked steeper trails. Requires some map reading skills.
Difficult - Scrambling, paths may be poorly defined. Regular use of hands for difficult sections. Cables may provide additional security on exposed sections. Falls in exposed sections may result in serious injury.
Hard - Rope needed to assure some short descents. Short climbing pitches of grade 3.x. normally good natural belay points available or pitches secured by cables. Falls in exposed sections may be fatal or will result in serious.
Extreme - Rope required to complete parts of the route or to assure ascent on exposed sections. Equivalent to grade 4.x climbing routes. Climbing helmet required due to exposure from rockfall (animals or other walkers). Falls in exposed sections will be fatal.
Warning: These gradings are given as a guide for dry conditions as we found them. Avalanches, mudslides and rockfall may change the difficulty of a given route. Thunderstorms are common in the afternoon in the mountains and temperatures can be freezing at 2000 meters even in the high summer. Check the weather conditions before you leave.