A 0.475 oz (14 ml), pen-sized spray bottle of 100% DEET insect repellent. 100% DEET is one of the most potent repellents available, so this stuff is your best option for the serious mosquito conditions in the High Sierra and environs. Be aware that concentrated DEET can dissolve many synthetic fabrics and plastics (be especially careful with sunglasses!), so apply with caution around your gear. Carrying a concentrated solution in this pen format is a smart way to trim weight from your through hiking or fast packing kit.