Cold Steel Sharkie Pocket - 91SP is a permanent marker, which is 7/8 inches thick and weighs 1.9 oz. the marker is made up of glass-reinforced plastic, which is usually used in the nightshades. The walls of this marker are at least four times thicker than the other markers. It was made for self-defense emergencies because it can become a stick to drive off the attacker. It is designed in such a way that the cap stays at its place and does not pop out like other markers. This marker is easy to carry and is very convenient to use as well.