NDS 4" Corrugate Hub Fitting. This black, high-density polyethylene (HDPE) adapter connects 4" single-wall corrugated pipe to 4" sewer and drain (S & D) pipe or fitting. It also connects the 4" slotted pipe in the EZflow Gravel-Free French Drain System (EZ-1001F) to 4" S & D pipe or fitting. With a maximum working pressure of 5 psi, it is suitable for non-pressurized underground sewer and drainage applications. Meets applicable ASTM standards and comes with a hassle-free limited lifetime warranty.