This adapter fits to an 42mm rubber eyepiece. Used smartphone is an iPhone 7.
Circle diameter of the mounting knobs is 40mm, so another eyepiece adapters can be designed, knob diameter is 3mm.

This adapter is usable for most of all swarovski binoculars and field glasses.

Updates:
2018-07-19:
Updated iPhone 7 adapter.stl that it fits better with a iPhone 7

2018-07-20
Updated Eyepiece.stl

Hypercube Evolution

No

Yes

0.2mm

30%

Printed with PETG, recommended colour is black to reduce reflections!