Buy a ★ Butterfly Knife Boreal Forest CSGO Steam Skin on Skins Exchange. Exterior: Field-Tested This is a custom-designed balisong, commonly known as a butterfly knife. The defining characteristic of this weapon is the fan-like opening of a freely pivoting blade, allowing rapid deployment or concealment. As a result, butterfly knives are outlawed in many countries. It has been painted using a forest camouflage hydrographic.