Grooved Top Bar/Grooved Bottom Bar Frames.
Carton of 10. 18% more wood in end bars ( Full 3/8" thickness) Grooved bottom bar is stronger and easier to use. Foundation is placed in frame in grooved bottom bar and top bar groove. Rigid foundation works best such as Perma-Dent or Rite Cell.
Fits 6 5/8 inch Supers