The BK7 Fresnel Rhomb Retarder features its application in broad band, achromatic retardation at the expense of bulk.
This product have the specifications of the following: its materials are BK7 Grade A optical glass, dimension tolerance is +0.0/-0.2mm, clear aperture is >80%, flatness is λ/10@ 632.8nm, surface quality is 20-10 scratch and dig, wavelength range is 400-2000 nm for BK7 Glass, bevel is 0.2mm to 0.5mm and free aperture is 10x10 mm.