Better dimensions (ISO sizes) The UseFill obturator ISO size matches the largest ISO file size taken to length in the canal. For example, if you finish the canal with a size 20 file, with an 04, 06, 08, or 10 taper, then fill with the Size 20 UseFill obturator. Use the UseFill tip size matching the tip size of your largest file. Radiopaque alpha-phase gutta percha The UseFill Obturators are made of radiopaque alpha-phase gutta percha. The ideal flow characteristics serve optimal obturation into the far corners of the root canal. Resulting in an excellent 3D fill. The extremely radiopaque material ensures a highly visibility on x-rays.