Compatibility:Holders Construction:Optical Resin CR39 Edge Blending:Hard Thickness:0.1' / 0.25cm Density:GND2 Filter: Up to 0.3, GND4 Filter: Up to 0.6 and GND8 Filter: Up to 0.9 Filter Factor:GND2 Filter: Up to 2 (1 stop), GND4 Filter: Up to 4 (2 stop) and GND8 Filter: Up to 8 (3 stop) Dimensions:3.3 x 3.9' / 8.38 x 9.91cm