Conoscopes are also called interference spheres or interference balls. The conoscope is a necessary tool for use with a polariscope. Our conoscope is a strain free glass ball held within a black plastic protective case with convenient handle. The conoscope is used for magnifying the view of the axis through a polariscope. The conoscope allows you to see 2-d representation of the 3-d interference of the axis within the gem. The axis and its visual image is also called the interference figure. Dimensions: 56 x 16 x 8 mm Lens: 15mm Warranty: 3 year!