The 4” to 2 ½” dual port Y splitter provides you with the ability to reduce a 4” port (with an adapter fitting -not included or a simple hose section – also not included) down into two separate 2 ½” hose lines. This is perfect for shops that have multiple machines with 2 ½” ports like sanders, benchtop band saws, router tables and more! The 4” end can be inserted into a 4” section of hose and secured by a hose clamp. Please note that the 4” end will not fit inside of standard 4” ports. It is designed to be inserted into standard 4” hose or dust collection couplers specifically made to fit 4” ports or flanges. The two separate 2 ½” ends of the fitting can be inserted into standard 2 ½” hose and secured by a hose clamp. Please note that the 2 ½” end will not fit inside of standard 2 ½” ports. It is designed to be inserted into standard 2 ½” hose or dust collection couplers specifically made to fit 2 ½” ports or flanges. The 4” to 2 ½” dual port Y splitter is ideal most any workshop that needs to split the dust collector airflow into separate smaller machinery. To reduce down from a 4” machine port, you will likely need to a 4”hose section (NOT included) or a 4” adapter/coupler for proper installation. Made from ABS plastic, this fitting is designed to stand up to prolonged daily workshop usage. Hose clamps are required for a proper seal and are NOT included with the fitting. PORT DIMENSIONS: 4” Nominal OD – 3.902” or 3-29/32”, ID 3.733” or 3-47/64” 2-1/2” Nominal OD – 2.5” or 2-1/2”, ID – 2.32” or 2-21/64” The 4” to 2 ½” dual port Y splitter provides you with the ability to reduce a 4” port (with an adapter fitting -not included or a simple hose section – also not included) down into two separate 2 ½” hose lines. This is perfect for shops that have multiple machines with 2 ½” ports like sanders, benchtop band saws, router tables and more!