In the vesicular transport model, the vesicle buds from the ER and travels to the ERGIC/cis-Golgi network with COPII coat proteins accompanying the vesicle. In the tubular transport model, cargo proteins are transported in a continuous interwoven tubular network instead of discrete vesicles. COPII proteins remain on the ER membrane and function as a gatekeeper restricting entry of secretory proteins into tubules. Reproduced from Tang and Ginsburg (12).