Inner cylinder has a 53mm OD and is designed to fit 53mm Protopasta spool side openings. Outer cylinder is 205 OD and designed to fit 203mm Protopasta spool side edge. For both, I recommend printing in spiral (vase) mode with a 1mm extrusion width, 0.2mm layer thickness, and 20mm/s speed. I printed these in HTPLA at 205C with a 0.4mm nozzle.