The 38mm mini hangers are specifically designed for use with Canadian Lumber Standard timber (CLS)
CLS is planed all round and rounded on all 4 corners - the sizes 3x2 and 4x2 CLS are 50x75mm and 50x100mm but 38x63mm and 38x89mm when machined hence the 38mm mini hanger size
Canadian Lumber Standard timber (CLS) is used in many places including partition walls and ceilings