An adjustable diameter mechanism includes a plurality of cylinder portions, each of the cylinder portions comprising an arcuate portion of a cylinder and extending along an arc of less than or about 120 degrees of a 360 degree circle and having an inner side and an outer side. The inner side of the cylinder portions are coupled to first ends of a scissors mechanism at a pivot point and a slot of the cylinder portions, the scissors mechanism having a first and a second piece pivotally coupled at a pivot coupling, respective second ends of the scissors mechanism coupled to a respective pair of threaded bolts engaged with a screw having opposing threads meeting at a central point thereof.