The "Wooster 4″ Super Doo-Z 1/2″ Nap Roller Cover" is a paint roller cover manufactured by Wooster Brush Company. Here's what each part of the name usually refers to.
Wooster: The brand name indicates that the product is created by the Wooster Brush Company, a well-known maker of painting tools and accessories.
4″: This likely relates to the width of the roller cover, which is 4 inches wide.
Wooster refers to this roller cover as part of the "Super Doo-Z" product range or series. It could indicate that it's an improved or high-performance version of their ordinary roller covers.