What makes this system work so well is the Tak compression ring to hold the eyepiece instead of clumsy thumbscrews that would need to protude through the body. The eyepiece is completely self-contained in the ocular holder inside of the camera holder. Two thumbscrews allow quick disconnection of the camera holder (which uses a standard T-mount) with the with the ocular holder. Note that this also allows rotation of the camera body about the optical axis. A third thumbscrew allows the camera tubes length to be extended as needed. Very solidly built, worth every penny. Mine only came with a 1.25 ocular holder, although the FS Series manual indicates that it should come with both a 1.25 and a 0.965 ocular adapter. Not an issue for me since I only have 1.25 oculars. The solid construction insures that the film/CCD plane will not tilt off-axis.