Rectangular prisms are used to deflect a beam of light through 90 or 180 degrees. This can be used as component to create various optical devices. BK-7 can be used for a range between the visible and infrared light. fused-silica an be used for a range between ultraviolet and infrared light. China star optics offers a wide range of different materials and different degree of precision prisms. "Specification of our right angle prism as follow: *Material BK7 glass or UV grade fused silica *Dimension Tolerances +/-0.1mm *Angle Tolerance +/-3’or30” *Clear Aperture 90% *Surface Quality:60/40 or 20/10 *Surface Flatness λ/8 or λ/4 @633nm *Chamfer 0.3+/-0.1mm *Coating Optional "