The right-angle prism is often used as a mirror, which enables light path folding 90. The total internal reflection, it can be used as like the retroreflector can make photorefractive 180. Right-angle prism can also be used together like beam offset applications parameters: Material: K9 Size tolerance: + /-0.15mm Surface Accuracy: lambda / 8 at 632.8nm finish :40-20 center deviation: 90% down side: 0.25mm × 45 °