Master Series Vault 3 Snap Neoprene Ball Stretcher. This ball stretcher is made from firm, flexible, and slightly stretchy Neoprene material, and features an adjustable snap closure for the perfect fit. The comfortable, cushiony Vault stretcher is a great enhancer for both beginners and advanced users. Measurements 2 inches wide, adjusts from 3.5 inches to 4.13 inches in circumference. Materials Neoprene, Metal. Color Black.