Quick view ABT, Inc. ABT Polydrain PolyWall II Sidewall Extensions Compare $270.19 PolyWall I Sidewall Extensions allow the designer or contractor to extend a continuous-sloping channel run from 98.1 ft. (30 m) to 294.3 ft. (90 m) without necessity of a catch basin or outlet.l Features Increases depth 14.2'" Technical information... Add to Wish List Add to My Wish List Create New Wish List