This 8" Full Screw Square Throat Pattern C-Clamp by Armstrong is designed for use where a super deep throat is required. The square throat offers up to 89% more capacity than other patterns. The forcing screw has a sliding handle and roll formed acme threads for greater strength, smoother running, reduced thread damage, and produces more clamping force with less effort. In order to insure a proper alignment with the screw, the anvil is produced to have a flat surface and also is extra large for greater gripping area. A heavy walled hub supports the forcing screw, reducing distortion. The swivel pad completely encircles the ball joint, providing permanent attachment as well as full swivel action. Meets or exceeds US Federal specification GGG-C-406D