Ecp Series ergonomic center pull-tab plugs offer the convenience of a center-pull tab plug in an ergonomic material. This Series is an excellent alternative to threaded plugs because it saves time and labor during instillation and removal of plugs. The tab is molded fully into the end and sidewalls of the plug so it does not break off during plug removal.:: a: 0.397, b: 0.41, C: 0.64, D: 0.28, E: 0.40.