The Rhino I OFS is a Heavy Duty Sch. 80 drain used as an Overflow Bottom Drain together with a vertical riser or as a Sidewall Return. This drain is also available with the standard cover plate. With the standard cover plate installed, you can convert back and forth between a standard drain and an overflow drain. Simply remove the cover and screw a 2", 3", or 4" riser pipe into the internally threaded drain flange. Here again these drains are constructed of the same Sch 80 heavy duty material as the other Rhino drain models.