2 x 6 Scupper Affords Maximum Cockpit Drainage. Can be adjusted to fit different transoms from 2.5" up to approximately 3.25" thick. 5 degree angle further enhances drainage. Backup lid allows unrestricted flow. Opening 1 5/8" x 1 5/8". Flange outside the transom measures 7.25" x 3.25". Flange on the cockpit side is made the same as the outside except it is flush with the floor for maximum drainage.