Globes are clear acrylic one piece injection blow molded. The are 6 inches in diameter with a minimum neckless opening size of 2.81 inches and a maximum opening of 4.5 inches. This is a custom cut and can not be returned. To request a custom opening, please enter the opening desired in the comments section at the bottom of the checkout page, or call 800-665-3594. If no custom opening is indicated, the globe will be sent with the minimum opening indicated in the description.