Plays a role in the organization of the endoplasmic reticulum exit sites (ERES), also known as transitional endoplasmic reticulum (tER). Required for secretory cargo traffic from the endoplasmic reticulum to the Golgi apparatus. Involved in peroxisome biogenesis. Regulates the transport of peroxisomal biogenesis factors PEX3 and PEX16 from the ER to peroxisomes. SEC16A and SEC16B are each present in multiple copies in a heteromeric complex. Localizes to endoplasmic reticulum exit sites (ERES), also known as transitional endoplasmic reticulum (tER). Belongs to the SEC16 family.