Armstrong's 4" Full Screw C-Clamp General Service Pattern is designed for use where the depth of a deep throat or the extreme strength of a heavy duty pattern are not required. The forcing screw has standard v threads, a square head and sliding handle while an extra large anvil creates a greater gripping area. This clamp's swivel pad completely encircles the ball joint providing permanent attachment as well as full swivel action. A heavy walled hub supports the forcing screw reducing distortion. The anvil is produced to insure a flat surface for proper alignment with the screw. Meets or exceeds US Federal Specifiation GGG-C-406D.