CowboyStudio Articulating Magic Friction Arm Small Super Clamp Crab Pliers Clip w/ Stud Adapter 1/4" and 3/8" Included Ideal for articulating magic friction arm Suitable for 1/4" and 3/8" screw heads. Grips round or flat surfaces; Stainless steel internal components Size: 2.12 x 3.12 x 0.88inch (when the clip close up L x W x H) Max jaw opening: 2.75inch; min jaw opening: 0.39inch