Product Name: N-Bk7 N-Bak4 H-K9l Porro Prisms Boro Prisms Model NO.: powell Customized: Customized Application: Telescope Material: Glass Shape: Porro Prisms Usage: Beam Split, Binoculars Type: Rectangular Prism Scratch & Dig: 80/50~20/10 Flatness: Lambda/8~ Lambda/2 Angle Tolerance: 5" ~5' Coating: Incident Face Ar Coated or Single Layer Mgf2 Edge: Rounded Origin: China HS Code: 9001909090 Product Description Porro prisms are variants of the standard 90° prism but used as a pair to displace and invert a beam. Porro prisms are widely used in binoculars where they orientate the image correctly and reduce the total length of the binoculars by a small amount.