The fastest adjusting frame clamp on the market. Completely knurled for good grip, the speed-clamping nuts are designed to let you make fast adjustments, yet hold securely when you tighten them.They are cross drilled to slide easily on the rods until they come up against a corner clamp; then their threads engage. To release them, you just have to back them off a turn or two and they are then free sliding again.The speed clamp includes four corners (strong, glass-filled nylon with brass inserts), four speed clamping nuts and four 1/4" UNC threaded rods that will clamp up to 585mm(23") square. To increase clamping capacity to 1,120mm(44") square or 1,650mm(65") by 585mm(23") rectangle, an extension set is included; it contains four 1/4" UNC threaded rods and four coupling nuts. The rods and coupling nuts have a black-oxide finish. Made in Canada.