This 10" WHITE Round Acrylic Globes is for post top fixtures. The globe measures 9 1/2" to the opening and is about 10" in diameter . This globe fits on an application requiring a 4" neckless globe. 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.