The pen worked good enough for me. The pen contains chalk powder which gets distributed onto the fabric by a thin tiny wheel, and as the wheel spins, it lets out a line of chalk onto the fabric. The wheel only spins one way, so it sometime gets a tiny bit annoying having the turn the pen around all the time. The chalk can be taken off the fabric with a damp cloth.
In really like this chalk pen. It makes a nice, clearly visible line.