Lotus Connect Store › Eisco Labs Acrylic Semicircular Block, 3 1/2"x9/16" (90x16mm) Eisco Labs Acrylic Semicircular Block, 3 1/2"x9/16" (90x16mm) $9.37 Polished sidesDurable for classroom useWorks well in ray box experiments (Eisco Labs part number PH0602A)works well with low power monochromatic light source90x16mm acrylic semicircular block for light refraction and geometrical optics experiments Quantity: Add To Cart Added! Polished sidesDurable for classroom useWorks well in ray box experiments (Eisco Labs part number PH0602A)works well with low power monochromatic light source90x16mm acrylic semicircular block for light refraction and geometrical optics experiments