This Brief deals with heat transfer and friction in plate and fin extended heat transfer enhancement surfaces. It examines Offset-Strip Fin (OSF), Enhancement Principle, Analytically Based Models for j and f vs. Re, Transition from Laminar to Turbulent Region, Correlations for j and f vs. Re, Use of OSF with Liquids, Effect of Percent Fin Offset, Effect of Burred Edges, Louver fin, heat transfer and friction correlations, flow structure in the louver fin  array, analytical model for heat transfer and friction, convex louver fin, wavy fin, 3D corrugated fin, perforated fin, pin fins and wire mesh, types of vortex generators, metal foam fin, plain fin, packings, numerical simulation of various types of fins.