8 inch Round Acrylic Clear Globe for post top fixtures or interior light fixtures. The globe measures 7 3/8 inch before the neck and 7 7/8 inch including neck. The necks outside diameter measures 3 15/16 inch and measures 3 3/8 inch inside diameter. These globes are meant to fit on a 4 inch fitter or ring secured with set screws. Please check your fixture or existing globe for reference. Acrylic is the type of material that they are made of. These globes are absolutely UV stabalized and resistant to UV rays. Acrylic is a material resistant to weathering and aging and has an exceptional brilliance. The shine does not diminish even after prolonged use, thanks to an optimum surface hardness.