By simply squeezing the body of the Molotow Aqua squeeze Pen you can easily regulate the amount of liquid you are applying to your surface. The tips are similar to that of an actual paint brush. They are refillable with fluid inks and water, making them an economical and sustainable solution for any artist. The set of 3 includes the 1 mm, 3 mm, and 4 mm nib pens. The set of 6 includes the 1 mm, 2 mm, 3 mm, 4 mm, 7 mm, and 10 mm nib pens. Also sold individually.