These hold down clamps are designed to be used with the standard UJK Technology T-tracks or the Dovetailed T-track but can also be used without. The star knob allows you to secure your work easily. Clamping width of 30mm for the deluxe and 20mm for the smaller clamp. Used with the UJK Technology T-Track gives a thickness capacity of up to 50mm. Excellent for making jigs.