This is for a set of hold down clamp for use with the T-slot rail These clamps are useful in many wood and metalworking applications for holding, positioning and securing work Apply clamping pressure anywhere along the recessed T-rail Slips into the T-rail and attaches quickly by turning the knob nut T-screw and threaded rod are 8mm Features: This is for a set of retaining clamp for use with the T-shaped rail. These clamps are useful in many woodworking and metalworking applications for holding, positioning and securing work. Apply clamping pressure anywhere along the recessed T-rail. Slides into the T-track and attaches quickly by turning the nut on the hand knob. The T-screw and threaded rod have an 8mm thread. Very versatile! Also ideal for bindings and bindings! Specifications: Main material: metal Main color: silver Thread Size: M8