RWG-100
Campbell RWG-100 Self-Clamping Wire & Pipe Protector for 6 in. Wall Casings
You will appreciate how the plastic edges are rounded off, so there are no sharp corners.
Campbell Self Clamping Adjustable Wire & Pipe Protector 4"-6" Wells (RWG-100) FS
I noticed Red Rubber Grease doesn't dry out or crack like some cheaper greases.