Is using the Professional Twist Style 400A version. It is high quality version, the obvious difference vs the others can be seen from the pictures.
Design protects electrode from damage. Fully insulated and protected springs.
High durability spring-loaded jaws clamp rods up to 6.4mm (0.252”)
Ergonomic design for heavy duty works with a comfortable fully insulated Nylon handle, fits comfortably in the palm and helps to decrease operator fatigue.
Reversible top and bottom insulators are made of superior thermo-set material for strength and durability at high-temperatures.