Armstrong's 12" C-Clamp Deep Throat Pattern is the most popular and versatile style C-Clamp. Its forcing screw has a sliding handle and has roll formed acme threads for greater strength, smoother running, reduced thread damage, producing more clamping force with less effort. The clamp's swivel pad completely encircles the ball joint providing permanent attachment as well as full swivel action and the extra large anvil creates a greater gripping area that is produced to insure a flat surface for proper alignment with the screw. Heavy walled hub supports forcing screw reducing distortion. This clamp meets or exceed US Federal Spec. GGG-C-406D.