WoodRiver® Dust Connection® 4" to 2-1/2" Reducer is an adapter that makes it possible to attach two hoses of different diameters together. A step down in size by a reducer increases air velocity near the machine where it's needed most. The economical fittings found in the WoodRiver Dust Connection series are designed to help build a high performance dust extraction system for your shop. Each of the fittings are made of ABS plastic (except for the aluminum blast gate), a material that is durable enough to withstand the abrasive nature of saw dust and wood fiber.Features: 4" to 2-1/2" ABS Reducer Tapered large end on one side fits inside most 4" dust collection hose Attach two dust collection hoses of different diameters together Increases air velocity near the machine where it is needed most (near the machine) Specifications: Small end: 2-1/2" outer diameter and 2-1/4" inner diameter Large end: 3.9" outer diameter and 3-11/16" inner Material: ABS plastic What's Included: (1) WoodRiver® Dust Connection® ABS Reducer Fitting for Dust Collection System - 4" to 2-1/2"- 4" to 2-1/2" Reducer