This Digital T ring is designed to allow you to fit any camera or other T-2 accessory (device with an T-2 M42x0.75 thread) onto your Hyperion Zoom eyepiece, just screw directly to the top of your eyepiece to utilise the external T-2 threads on this adapter.
It has an 11mm optical length

Please note this is for MkI and MkII Zooms only, it will not work with MkIII Zooms