2 Prong Adjustable Universal Clamp with an adjustable 7.5"-8" length This clamp with boss head is ideal for use with straight sides glassware apparatus such as tubes, flask necks, and burettes Accommodates objects up to 3" and has non-slip vinyl coated rubber prongs Adjustable thumb screws on both sides allows for a wider range of accommodation 8" length, 4" width, 1" boss head opening This 2 Prong Double Adjustable Universal Clamp features an integral boss head and non-slip vinyl coated jaws. The item has an adjustable length of 7.5"-8" and has a width of 4" at the thumb screws. The jaws measure 2" long and open 3" wide, and the jaws are adjustable on both sides with thumb screws. This clamp with boss head is ideal for use with straight sides glassware apparatus such as tubes, flask necks, and burettes.