There are many 1.25" and 2" star diagonals on the market. Many of them have a mediocre mirror quality with 90% reflectivity (10% loss) and a plastic body.  These diagonals by SVBONY stand for a high-quality alternative to those cheap parts. It offers excellent image and mechanical quality. There's no vignetting over the full field. SV188P features sophisticated, Multi-layered dielectric coatings that provide an astounding 99% reflectivity for maximum view brightness and sharpness.

SV188P Diagonals provides a comfortable 90-degree viewing orientation when observing the night sky through a refractor. When use the SV188P with Maksutov-Cassegrain (Mak-Cass) or Schmidt-Cassegrain telescope, you need a special adapter. 

Another advantage is the nosepiece barrel is threaded to accept 1.25" and 2" filters (based on the diagonal model size). Brass lock Screw and Brass Compression Rings feature more precision and prevent barrels or the surface of eyepieces from marring and scratching.

Specifications