well made with big convenient set screws
I've been buying more TPO accessories this past year and this is another one that impresses me with the excellent build quality.
perfect fit for eyepieces and other xtension tubes.
Fit and finish are very good. Seating plane and shoulder are parallel to within 0.01 mm or less. Internal thread intended to minimize reflections is reasonably effective.
received in good order. Was necessary with the TPO 12" f/4 tube assy.