If what you are looking for is the highest achievable brightness contrast and sharpness during critical observations with high-end instruments WO 90-degree 2" mirror Dielectric star Diagonal is your choice. This dielectric diagonal features 100% real carbon fiber side plates that add that touch of class your scope deserves. A premium product at a discounted price. Check it out and see the difference between a "budget diagonal" and a real bargain!Free SCT adapter with each diagonalIncluded in the price you will have an SCT ring that makes your diagonal work on SC telescopes or our ZS66 series as well! Get one diagonal use it on ANY telescope! This alone is worth US $40 and will save you the costs of buying another diagonal!Top-Notch Performance and brightnessDielectric coating allows 99% reflectivity.10 mm thick substrate flat for optimal image stability.Polished to 1/10th wave accuracy. Pre-coated Flat AccuracyAccurate design guarantees constant alignment. No further alignment needed.Meticulous Craftsmanship2" to 1.25" eyepiece adapter included.Lock screw for eyepiece/adapter.Big knurled thumbscrews easy to turn even with gloves on.Strikingly beautifulPatented elegant design. High-quality machining out of the best aluminum.Internally antireflection threaded for highest contrast.Superbly ConstructedCompression rings (both on diagonal and adapter) to prevent barrels marring.Internal safety stop prevents 2" barrels from hitting the mirror.Why W.O. diagonals do not feature an Adjustable alignment system?Having an adjustable alignment system is an admission that the diagonal can go out of collimation due to poor mechanical construction. Thanks to the patented design of WO diagonals you will always have a diagonal that performs perfectly like the first day you got one!