- 6mm ---- 5 pieces of glass - 9mm ---- 6 pieces of glass - 15mm ---- 4 pieces of glass - 20mm ---- 5 pieces of glass Wide - Angle UW68° Series - Metallic appearance · Multi - layer coating on optical lenses · Wide - angle design for large field of view ULTRA WIDE ANGLE COMPLEX COLOR DIFFERENCE DESIGN Product Name: UW68°6mm; Focal Length: 6mm; Angle: 68°; Coating: Multi - layer coating; Interface: 1.25 inches; Lens Diameter: 21mm Product Name: UW68°9mm; Focal Length: 9mm; Angle: 68°; Coating: Multi - layer coating; Interface: 1.25 inches; Lens Diameter: 21mm Product Name: UW68°15mm; Focal Length: 15mm; Angle: 68°; Coating: Multi - layer coating; Interface: 1.25 inches; Lens Diameter: 21mm Product Name: UW68°20mm; Focal Length: 20mm; Angle: 68°; Coating: Multi - layer coating; Interface: 1.25 inches; Lens Diameter: 24mm The eyepiece comes with a dust cover, and there is an error of 1 - 3 cm in manual measurement.