An experimental study has been carried out to investigate the heat transfer and pressure drop characteristics of flat tube heat exchangers with plain, wavy, louvered and offset strip fin surfaces. Results are presented as plots of Colburn j factor and friction factor f against Reynolds in the range of 600-6500. Additionally, the dimensional heat transfer coefficient and pressure drop are presented as a function of frontal air velocity. Finally, two comparison methods are adopted to evaluate the air side performance of the plain fin, wavy fin, louvered fin and offset strip fin surface. The results show that the offset strip fin has the best performance of heat transfer enhancement.