This is taken from the Shooting Wire:
"The LensPen® is essential to keeping binoculars and all kinds of optics ready for maximum performance. It's so simple, so effective and so dependable.
Small enough that you can clip it in your pocket or toss it in your case, the LensPen has two easily accessible working ends. Slide out the brush end first and use it to effectively remove all loose dust and dirt from the lens or eyepiece. The retractable brush, made from natural goat hair, is so gentle it can do no damage to the optics, yet it's so hard-working the dust vanishes."