Metal Head 04 RSP is a squeezable marker, equipped with a metalhead and 4 mm built-in ball that can write on almost every surface in all conditions. Try it on rust for example! The soft plastic body makes it possible to squeeze it and controll the amont of paint that comes out. Metal Head 04 RSP includes an extra-permanent concentrates of "Full Metal Paint", which is almost impossible to remove once it dries.