Neither the G2 or the G3 Can Be Used with the 37mm, 50mm, 75mm or the 500mm
It Has an Insert for Filters of 76.2mm (3”) on the Lens Side
The G2 Accepts Unmounted Gelatin Filters Only Because the Insert Is Really Thin
G2 and G3 Compendium Shades have an Insert for Larger Filters at the Front. Only Thin Gelatin Ones Are Accepted. The G2 Accepts 102mm (4”) Filters, While the G3 Accepts 125mm (4.8”) Filters.