These flanges are used to connect a dust collection hose to the underside of a table saw, jointer, or any machine for that matter. The opening will accept a 4” flexible hose using a hose clamp or tapered a quick connect fitting. These ABS plastic flanges are very economically priced to allow you to outfit your dust collection system for maximum performance. These fittings are abrasion resistant and are designed to withstand the abrasive nature of wood chips and saw dust. Due to the potential for built up of static electricity, it is recommended that all dust collection systems with plastic fittings be properly grounded.