Black and white vinyl sticker that says "SK to all sources of QRM for working people". SK is ham radio-speak for "silent key" and is often used as a euphemism for death. E.g. "Bob is a silent key now." QRM is a ham radio "Q code"that stands for noise or interference. Altogether it means "death to all sources of interference for working people", a ham radio specific take on the Makhnovist flag which read "Death to all those who stand in the way of freedom for working people." Proceeds go toward buying physical copies of license exam study materials.