Widefield 5x, 10x, 15x, or 20x eyepieces, paired. 30.5mm diameter. For use with National Optical models:
- 400 Series
- 405 Series
- 409 Series
- 410 Series
- 411 Series
- 415 Series
- 416 Series
- 417 Series
- 420 Series
- 420T Series
- 430 Series
- 446 Series
- 447 Series
- 448 Series
- 460 Series
- DC3-420T
- DC5-420T