The smooth one - EZ Flush Standard has 30 pct more coils than other standard or regular drain hose which produces a smoother interior, reducing waste hang-ups. 30 pct more coils also means 30 pct more wire for more crush resistance. Made of the highest quality vinyl to resist cracking and checking as a result of toilet chemicals and extreme temperatures. Remains flexible and easy to use in all weather conditions.Includes factory installed sizing rings for hassle-free adapter installation. Sizing rings keep hose end fully expanded. To attach hose fittings, simply remove sizing ring and attach hose fitting as usual.