If what you are looking for is the highest achievable brightness, contrast and sharpness during critical observations with high-end instruments, The WO 90° 2 inch mirror Dielectric star Diagonal is your choice. A premium product at a discounted price!
Ultra High Dielectric 99% reflectivity Precision 1/10 lambda surface with 10mm-thick mirror. 2"- 1.25" adapter with brass clamping ring. Inside diameter (48mm): threaded to fit a variety of filters. Weight : 470 g CF Body