The Junior Clamp has a mouth opening of 1.75 inches and can attach to both flat and round tubes. It has a 1/4"-20 and 3/8"-16 threaded holes that allow you to attach a variety of accessories such as an articulating arm. The Junior Clamp has a reinforced rubber lining on the mouth that allows for a no-slip grip. This clamp is strong yet small in size and is easily stored in the pocket of your kit bag or clothing.