I am a beginner and I have not used the best, most expensive of anything yet. However, this diagonal has a beautiful finish and eyepieces slide in and out smoothly. It threads on easily and holds tight.
Because it treads on to the OTA, this is the best diagonal for a SCT. It is secure, and won't fall off if you use it as a handle. Eyepieces lock tight. Optically it is excellent.
Fit and finish are excellent and right at home in the edge 8.I also bought a Williams optics 40mm 2 inch eyepiece to go with it,they really expand the field of view in the edge 8 hd.Very satisfied with results!!