Neewer 5-Pack Set Muslin Holder Spring Clamps Clips for Photo Studio Backdrops Backgrounds Nice for stretching out the wrinkles from muslin backgrounds. Small teeth on the inner diameter hold muslin cloth or paper backdrops in place for photo work. Heavy duty metal construction keeps things extra secure and damage-free. Used on crossbar (Diameter&lt; 11"/28mm). Maximum load: 5lbs/2.3kg