diff --git a/modules/serverbidBidAdapter.js b/modules/serverbidBidAdapter.js
index 2b1de9a9a89..24bb5aa6255 100644
--- a/modules/serverbidBidAdapter.js
+++ b/modules/serverbidBidAdapter.js
@@ -24,6 +24,9 @@ const CONFIG = {
   }
 };
 
+let siteId = 0;
+let bidder = 'serverbid';
+
 export const spec = {
   code: BIDDER_CODE,
   aliases: ['connectad', 'onefiftytwo', 'insticator', 'adsparc', 'automatad'],
@@ -62,6 +65,10 @@ export const spec = {
 
     let ENDPOINT_URL;
 
+    // These variables are used in creating the user sync URL.
+    siteId = validBidRequests[0].params.siteId;
+    bidder = validBidRequests[0].params.bidder;
+
     const data = Object.assign({
       placements: [],
       time: Date.now(),
@@ -140,7 +147,21 @@ export const spec = {
   },
 
   getUserSyncs: function(syncOptions) {
-    return [];
+    if (syncOptions.iframeEnabled) {
+      if (bidder === 'connectad') {
+        return [{
+          type: 'iframe',
+          url: '//cdn.connectad.io/connectmyusers.php'
+        }];
+      } else {
+        return [{
+          type: 'iframe',
+          url: '//s.zkcdn.net/ss/' + siteId + '.html'
+        }];
+      }
+    } else {
+      utils.logWarn(bidder + ': Please enable iframe based user syncing.');
+    }
   }
 };
 
@@ -185,6 +206,9 @@ sizeMap[429] = '486x60';
 sizeMap[374] = '700x500';
 sizeMap[934] = '300x1050';
 sizeMap[1578] = '320x100';
+sizeMap[331] = '320x250';
+sizeMap[3301] = '320x267';
+sizeMap[2730] = '728x250';
 
 function getSize(sizes) {
   const result = [];
diff --git a/test/spec/modules/serverbidBidAdapter_spec.js b/test/spec/modules/serverbidBidAdapter_spec.js
index fb31f925c6e..d3dc64ae6df 100644
--- a/test/spec/modules/serverbidBidAdapter_spec.js
+++ b/test/spec/modules/serverbidBidAdapter_spec.js
@@ -245,10 +245,10 @@ describe('Serverbid BidAdapter', () => {
       expect(opts).to.be.empty;
     });
 
-    it('should always return empty array', () => {
+    it('should return a sync url if iframe syncs are enabled', () => {
       let opts = spec.getUserSyncs(syncOptions);
 
-      expect(opts).to.be.empty;
+      expect(opts.length).to.equal(1);
     });
   });
 });