These two piece clamps are used for special installations only, such as hand dug wells, cisterns or other crazy circumstances.  Generally you will need two, one above and one below the lid or cap you are using.  They grip 3/4" PVC pipe very tightly.  Aluminum, 1-1/16" ID x 1-7/8" OD x 1/2" with two set screws, blue pipe not included.