diff --git a/tools_webrtc/ios/client.webrtc/iOS32_Sim_Debug_(iOS_9.0).json b/tools_webrtc/ios/client.webrtc/iOS32_Sim_Debug_(iOS_9.0).json
index 6bc6f8e9ed..1ba462bbc5 100644
--- a/tools_webrtc/ios/client.webrtc/iOS32_Sim_Debug_(iOS_9.0).json
+++ b/tools_webrtc/ios/client.webrtc/iOS32_Sim_Debug_(iOS_9.0).json
@@ -20,11 +20,8 @@
       "include": "common_tests.json",
       "device type": "iPhone 5",
       "os": "9.3",
-      "dimensions": [
-        { "os": "Mac-10.13.4", "pool": "Chrome" },
-        { "os": "Mac-10.13.5", "pool": "Chrome" },
-        { "os": "Mac-10.13.6", "pool": "Chrome" }
-      ],
+      "host os": "Mac-10.13",
+      "pool": "Chrome",
       "priority": 30
     }
   ]
diff --git a/tools_webrtc/ios/client.webrtc/iOS64_Sim_Debug_(iOS_10.0).json b/tools_webrtc/ios/client.webrtc/iOS64_Sim_Debug_(iOS_10.0).json
index 54f8301601..f9ed62c7fe 100644
--- a/tools_webrtc/ios/client.webrtc/iOS64_Sim_Debug_(iOS_10.0).json
+++ b/tools_webrtc/ios/client.webrtc/iOS64_Sim_Debug_(iOS_10.0).json
@@ -20,17 +20,8 @@
       "include": "common_tests.json",
       "device type": "iPhone 6s",
       "os": "10.3",
-      "xcode build version": "8E3004b",
-      "dimensions": [
-        {
-          "os": "Mac-10.12",
-          "pool": "Chrome"
-        },
-        {
-          "os": "Mac-10.13.3",
-          "pool": "Chrome"
-        }
-      ],
+      "host os": "Mac-10.13",
+      "pool": "Chrome",
       "priority": 30
     }
   ]
diff --git a/tools_webrtc/ios/client.webrtc/iOS64_Sim_Debug_(iOS_11.0).json b/tools_webrtc/ios/client.webrtc/iOS64_Sim_Debug_(iOS_11.0).json
index a139dd86ca..8eee4978ab 100644
--- a/tools_webrtc/ios/client.webrtc/iOS64_Sim_Debug_(iOS_11.0).json
+++ b/tools_webrtc/ios/client.webrtc/iOS64_Sim_Debug_(iOS_11.0).json
@@ -20,11 +20,8 @@
       "include": "common_tests.json",
       "device type": "iPhone 7",
       "os": "11.0",
-      "dimensions": [
-        { "os": "Mac-10.13.4", "pool": "Chrome" },
-        { "os": "Mac-10.13.5", "pool": "Chrome" },
-        { "os": "Mac-10.13.6", "pool": "Chrome" }
-      ],
+      "host os": "Mac-10.13",
+      "pool": "Chrome",
       "priority": 30
     }
   ]
diff --git a/tools_webrtc/ios/client.webrtc/iOS64_Sim_Debug_(iOS_9.0).json b/tools_webrtc/ios/client.webrtc/iOS64_Sim_Debug_(iOS_9.0).json
index d4c989b349..2217673ea9 100644
--- a/tools_webrtc/ios/client.webrtc/iOS64_Sim_Debug_(iOS_9.0).json
+++ b/tools_webrtc/ios/client.webrtc/iOS64_Sim_Debug_(iOS_9.0).json
@@ -20,11 +20,8 @@
       "include": "common_tests.json",
       "device type": "iPhone 6s",
       "os": "9.3",
-      "dimensions": [
-        { "os": "Mac-10.13.4", "pool": "Chrome" },
-        { "os": "Mac-10.13.5", "pool": "Chrome" },
-        { "os": "Mac-10.13.6", "pool": "Chrome" }
-      ],
+      "host os": "Mac-10.13",
+      "pool": "Chrome",
       "priority": 30
     }
   ]
diff --git a/tools_webrtc/ios/tryserver.webrtc/ios_sim_x64_dbg_ios10.json b/tools_webrtc/ios/tryserver.webrtc/ios_sim_x64_dbg_ios10.json
index d5f77bad94..ebb445b159 100644
--- a/tools_webrtc/ios/tryserver.webrtc/ios_sim_x64_dbg_ios10.json
+++ b/tools_webrtc/ios/tryserver.webrtc/ios_sim_x64_dbg_ios10.json
@@ -21,11 +21,8 @@
       "include": "common_tests.json",
       "device type": "iPhone 6s",
       "os": "10.3",
-      "dimensions": [
-        { "os": "Mac-10.13.4", "pool": "Chrome" },
-        { "os": "Mac-10.13.5", "pool": "Chrome" },
-        { "os": "Mac-10.13.6", "pool": "Chrome" }
-      ],
+      "host os": "Mac-10.13",
+      "pool": "Chrome",
       "priority": 30
     }
   ]
diff --git a/tools_webrtc/ios/tryserver.webrtc/ios_sim_x64_dbg_ios11.json b/tools_webrtc/ios/tryserver.webrtc/ios_sim_x64_dbg_ios11.json
index 90c4212690..a5208088ae 100644
--- a/tools_webrtc/ios/tryserver.webrtc/ios_sim_x64_dbg_ios11.json
+++ b/tools_webrtc/ios/tryserver.webrtc/ios_sim_x64_dbg_ios11.json
@@ -21,11 +21,8 @@
       "include": "common_tests.json",
       "device type": "iPhone 7",
       "os": "11.4",
-      "dimensions": [
-        { "os": "Mac-10.13.4", "pool": "Chrome" },
-        { "os": "Mac-10.13.5", "pool": "Chrome" },
-        { "os": "Mac-10.13.6", "pool": "Chrome" }
-      ],
+      "host os": "Mac-10.13",
+      "pool": "Chrome",
       "priority": 30
     }
   ]
diff --git a/tools_webrtc/ios/tryserver.webrtc/ios_sim_x64_dbg_ios9.json b/tools_webrtc/ios/tryserver.webrtc/ios_sim_x64_dbg_ios9.json
index c639ba756b..68b9d7c9bd 100644
--- a/tools_webrtc/ios/tryserver.webrtc/ios_sim_x64_dbg_ios9.json
+++ b/tools_webrtc/ios/tryserver.webrtc/ios_sim_x64_dbg_ios9.json
@@ -21,11 +21,8 @@
       "include": "common_tests.json",
       "device type": "iPhone 6s",
       "os": "9.3",
-      "dimensions": [
-        { "os": "Mac-10.13.4", "pool": "Chrome" },
-        { "os": "Mac-10.13.5", "pool": "Chrome" },
-        { "os": "Mac-10.13.6", "pool": "Chrome" }
-      ],
+      "host os": "Mac-10.13",
+      "pool": "Chrome",
       "priority": 30
     }
   ]
diff --git a/tools_webrtc/ios/tryserver.webrtc/ios_sim_x86_dbg_ios9.json b/tools_webrtc/ios/tryserver.webrtc/ios_sim_x86_dbg_ios9.json
index e55519fc76..48eb409eaa 100644
--- a/tools_webrtc/ios/tryserver.webrtc/ios_sim_x86_dbg_ios9.json
+++ b/tools_webrtc/ios/tryserver.webrtc/ios_sim_x86_dbg_ios9.json
@@ -21,11 +21,8 @@
       "include": "common_tests.json",
       "device type": "iPhone 5",
       "os": "9.3",
-      "dimensions": [
-        { "os": "Mac-10.13.4", "pool": "Chrome" },
-        { "os": "Mac-10.13.5", "pool": "Chrome" },
-        { "os": "Mac-10.13.6", "pool": "Chrome" }
-      ],
+      "host os": "Mac-10.13",
+      "pool": "Chrome",
       "priority": 30
     }
   ]