diff --git a/rattail_corepos/importing/corepos/api.py b/rattail_corepos/importing/corepos/api.py
index a87bcc2..98628c7 100644
--- a/rattail_corepos/importing/corepos/api.py
+++ b/rattail_corepos/importing/corepos/api.py
@@ -454,6 +454,7 @@ class ProductImporter(FromCOREPOSAPI, corepos_importing.model.ProductImporter):
         'food_stampable',
         # 'tax1',
         # 'tax2',
+        'case_size',
     ]
 
     def setup(self):
@@ -467,6 +468,14 @@ class ProductImporter(FromCOREPOSAPI, corepos_importing.model.ProductImporter):
         self.core_existing = self.cache_model(model.Product, key='corepos_id',
                                               query=query)
 
+        self.vendor_items_by_upc = {}
+
+        def cache(item, i):
+            self.vendor_items_by_upc.setdefault(item['upc'], []).append(item)
+
+        self.progress_loop(cache, self.api.get_vendor_items(),
+                           message="Caching CORE Vendor Items")
+
     def get_host_objects(self):
         return self.api.get_products()
 
@@ -501,6 +510,12 @@ class ProductImporter(FromCOREPOSAPI, corepos_importing.model.ProductImporter):
             return product.uuid
         return get_uuid()
 
+    def get_vendor_items(self, api_product):
+        if hasattr(self, 'vendor_items_by_upc'):
+            return self.vendor_items_by_upc.get(api_product['upc'])
+
+        return self.api.get_vendor_items(upc=api_product['upc'])
+
     def normalize_host_object(self, product):
         try:
             upc = GPC(product['upc'], calc_check_digit='upc')
@@ -552,6 +567,23 @@ class ProductImporter(FromCOREPOSAPI, corepos_importing.model.ProductImporter):
                 'uom_abbreviation': size_info['uom_abbrev'],
             })
 
+        if 'case_size' in self.fields:
+            case_size = None
+            items = self.get_vendor_items(product)
+            if items:
+                # here we sort by `modified DESC` to get the "deterministic
+                # pseudo-default" vendorItems record
+
+                def sortkey(item):
+                    dt = datetime.datetime.strptime(item['modified'], '%Y-%m-%d %H:%M:%S')
+                    return dt
+
+                items = sorted(items, key=sortkey, reverse=True)
+                item = items[0]
+                case_size = decimal.Decimal(item['units'])
+
+            data['case_size'] = case_size
+
         return data