All brass and steel components make the Bullet pen virtually indestructible. When closed, the Bullet Space pen fits cleanly in any pocket, backpack or coin-purse. Great in front pants pocket because it won't jab you when sitting down into a car seat. The nitrogen powered pressurized refill inside the Space Pen will enable it to write in extreme freezing cold temperatures down to -55F and boiling heat, to +400F. Space Pens will also write through water, dirt, oil and on shiny surfaces such as glass or tile. Lifetime Guarantee!