Cheeseborough Clamp Sets - these clamps are for attaching to 2 inch OD lighting truss or 1-1/2 inch Schedule 40 pipe (1.9 inch OD). [break] They are very useful for speaker rigging from generic lighting truss, theatrical lighting pipes, or batten. Full cheesborough swivel clamps are used for joining two pipes together. [break] Pro audio rigging design, roof attachment, supplemental structure, sales, support and PE stamped drawings in any US State provided by Polar Focus. Call us today for more information at (413) 586-4444.