Here we have 2 Hemingray- 518 Spools. The one on the left is threaded inside while the other has a metal insert. The threaded one has a circumferance of 6 5/8" while the other has a circ. of 7". The pin hole of the threaded one is 7/8" and the other has a pinhole of 6/8". These are 2 intersting pieces and raise some interesting questions as to why Hemingray would make these so differently. Any comments on the threaded one? I have never seen anything like that before. It sure is an oddball.