Lightweight walking pantsLightweight nylon pants are recommended while trekking. They are air permeable, dry quickly and provide sun protection.You can have convertible ones as it can get hot in the afternoons.Fleece or tracksuit pantsYou will be experiencing temperature fluctuations throughout the trekking period. Thus, you can wear track pants around the tea house and for sleeping.Waterproof shell pantsIf you are going for a trek in the rainy or winter seasons, you will face some rain or snow. So, you will need waterproof or windproof shell pants to keep yourself dry.