Common imaging train

Sony E (α7 / α6000 series) on a T-ring

The Starizona Apex ED 0.65× is one of the few reducers with a T2 (M42) output, which is why it pairs so simply with a T-ring or a T2-fronted camera — and why its 30 mm image circle suits small sensors. The 55 mm convention exists because of DSLRs: a T-ring is cut so that the sensor sits 55 mm behind its T2 thread, whatever the body's own flange distance. So a T2-threaded flattener plus a T-ring is complete with nothing in between. The catch is the thread itself — the 38 mm T2 bore clips the corners of a full-frame sensor. Full-frame α7 bodies hit the T2 bore limit; crop-sensor α6000 bodies do not.