Porro prisms can be used as a 180＜ beam folding application. An antireflection coating on the hypotenuse improves efficiency of the prism as a retroreflector as long as acceptance limitations for TIR on the roof faces are not exceeded.

 
 
BTMT can provide for any sizes:
，The roof angle accuracy is less than 2 arc seconds
，No bevel on the roof and the width of roof is less than 5
　micron
，The symmetry of roof line is less than 0.05
，The ratio of length and diameter can be met 1.5.
，The demission tolerance is within 0.05mm
，The Surface Accuracy can be ensured λ/10 @632.8nm
，The Surface quality can be met 10/5 and 20/10.
，Material includes BK7, UVFS and IR FS.