Retroreflectors reflect an image or beam back toward its original direction via three reflections. The beam or image will be inverted and reflected through 180° even if the angle of incidence is not zero. The insensitivity of the alignment of these prisms make them ideal retroreflecting optics. For these retroreflecting prisms, the incident and reflected beams will be parallel to within 3 arcsec. However, unless the incident and reflected beams strike the exact center of the optic, they will not overlap but rather be shifted with respect to each other. For example, if the incident beam strikes the optic 3 mm to the right of center, the retroreflected beam will emerge 3 mm to the left of center.These retroreflectors are widely used for survey industry.

Specifications:
Material: K9/Fused silica
Dimension Tolerance: +0/-0.1mm 
Surface Quality: 40/20  
Wavefront Distortion: λ/8 at 632.8 nm
Comprehensive Angular accuracy：2-10"
Bevel: Protective bevel
Coating: Reflective coating&AR coating(+Black paint)

Highly recommended retroreflector list from Yutai Optics:
H-K9L(BK7) Retroreflector,
UV Fused Silica Retroreflector,
2",3",5"Retroreflector,
Retroreflector with Au,Al,Cu Coating and black paint,
Retroreflector with a edge removed
Dia.12.7mm/25.4mm/38.1mm/64mm Retroreflector,
Related GR24,GPR1/GPH1,360°(Mini) Prisms,L-bar prism.