Our pen scratch brush is made of a durable plastic construction with a metal pen tip. The brush length exposure is adjustable by the turning of a knob on the end of the brush holder. The overall length of the tool is 4-1/2" with a cleaning tip that is 3/16" in diameter. Select from four different refillable brush materials: Fiberglass, Steel, Nylon, and Brass. Each refill is 3/16" in diameter and has a useable length of 1-1/4". All of the refills can be interchanged into any of the brush bodies.