This reducer - flattener is designed to work with the Altair Astro Wave Series 115mm EDT-X FPL53 102mm F7 Super ED Triplet APO.
It consists of two components:
The flattener body containing the optics, with M92 male outer thread on the telescope side and M72 female inner thread on the camera side
An M72 to M48 adaptor-spacer with M72 male outer thread on the flattener side and M48 male outer thread on the camera side. The adaptor has a 21.62mm optical length, to give 55mm sensor to flange distance.
This field flattener is designed to work with the Altair Astro Wave 115ED Triplet refractors with 3.7" focuser. It has an M48 rear thread adaptor for connecting your DSLR or CCD camera giving 55mm distance to the camera sensor.