MS3 - Soft / Intermediate Terrain. MH3 - Intermediate / Hard Terrain. For the M12 and S12 tires, the sizes are as follows: 100/100-18 = Michelin size of 120/90/18. 100/90-19 = Michelin size of 120/80-19. 80/100-21 = Michelin size of 90/90-21. Note: Please check your current tire size to ensure you are ordering the correct replacement size.
"These tires are the best set up I have found for the terrain I ride on. I live in CO and these tires hold up under the most difficult terrain without chunking and have a great tread pattern. I would highly reccomend them and are my favorite tires for where I ride."