This is a popular pen everyone seems to not get enough of. The bolt on the pen is what activates the clicking mechanism. They are made of metal with a hand crafted wood barrel. The cartridges are replaceable in these pens. Choose which number of metal and wood you would like your pen to be made with and put it in the description when you order. You can also order this pen with an acrylic barrel however that will cost extra and more description will be needed for what color you wish it to be.